CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Not applicable. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not applicable. REFERENCE TO A COMPACT DISK APPENDIX [0003] Not applicable. BACKGROUND OF THE INVENTION [0004] Post-translational modifications of proteins, such as post-translational sulfation, have been shown to be regulators of protein function. Sulfation occurs on tyrosine or on carbohydrate chains (glycans) within glycoproteins and frequently generates specific epitopes that can be recognized by growth factors, extracellular matrix proteins, cell surface receptors and viruses. Sulfation-dependent adhesion underlies physiological and pathological processes such as lymphocyte recirculation through lymph nodes, migration of leukocytes to sites of chronic inflammation, and viral infection. Carbohydrate sulfation and protein sulfation are extracellular modifications that contribute to a variety of biological recognition events at the cell surface and in the extracellular matrix. See Hooper et al. (1996, FASEB J., 10:1137-1 146); Bowman et al. (1999, Chem Biol., 6:R9-22); Fukuda (2001 , J. Biol. Chem., 276:47747-47750); and Lee et al. (2003, Glycobiology, vol. 13:245-254). Hemmerich, S. (2000, Glycobiology, 10:849-56); Hemmerich, S. 2001, (Drug Discov. Today) 6:27-35. [0005] Sulfation also functions in the metabolism of xenobiotic compounds, steroid biosynthesis, and modulating the biological activity, inactivation and elimination of potent endogenous chemicals such as thyroid hormones, steroids and catechols. This pathway is reversible, comprising the sulfotransferase enzymes that cause the sulfation and the sulfatases that hydrolyze the sulfate esters formed by the action of the sulfotransferases. Accordingly, the interplay between these sulfotransferases and sulfatases regulates the availability and activity of biological molecules. [0006] Various assays for sulfotransferase and sulfatase activity have been described in Ramaswamy et al. (1987, Methods of Enzymology, vol.143: 201-207); Bistrup et al. (U.S. Pat. No. 6,265,192); Wong and Burkart (U.S. Pat. 6,255,088); Fukuda et al. (U.S. Pat. Application No. 2002/0061562); PCT publication WO 01/06015; and U.S. Pat. Application No. 2003/0147875. Additional protocols that assay sulfotransferase activity have been described by To and Wells (1984, J. Chrom., 301 : 282-287); Honkasalo and Nissinen (1988, J. Chrom., 424: 136-140); Sim and Hsu (1990, J. Pharm. Meth., 24: 157-163); Bhakta et al. (2000, J. of Biol. Chem, 275:40226-40234); and Verdugo D., et al. (2002, Anal. Biochem., 307:330-336). In spite of the above disclosures, there remains a need for methods for screening for agents that modulate the activity of enzymes associated with sulfation, such as sulfotransferases and sulfatases, that are safer and/or less expensive and/or more convenient to use, and/or adaptable to high throughput screening applications. [0007] All references, patents, patent publications and patent applications disclosed herein are hereby incorporated by reference in their entirety. BRIEF SUMMARY OF THE INVENTION [0008] The present invention relates to methods for screening for agents that modulate the activity of an enzyme associated with sulfation of biological molecules, such as sulfotransferases and sulfatases. In some examples, the methods comprise combining a sulfotransferase polypeptide, or sulfatase polypeptide, with an appropriate acceptor and a test agent under conditions suitable for activity, wherein the sulfotransferase polypeptide is capable of transferring a sulfate moiety from a sulfate donor to an appropriate acceptor and the sulfatase polypeptide is capable of releasing a sulfate moiety from an appropriate acceptor; and separating acceptor in the reaction from acceptor acted on by the sulfotransferase polypeptide or sulfatase polypeptide based on charge differential. In some examples, when the enzyme is a sulfotransferase polypeptide, the acceptor in the reaction is non-sulfated, has a more neutral charge than acceptor acted on by the sulfotransferase polypeptide or has a neutral charge (that is, is not charged) and the action of the sulfotransferase polypeptide adds at least one sulfate moiety to the acceptor. In other examples, when the enzyme is a sulfatase polypeptide, the acceptor in the reaction comprises at least one sulfate moiety, has a more negative charge than the acceptor lacking a sulfate moiety, or is negatively charged and the action of the sulfatase polypeptide releases at least one sulfate moiety from the acceptor, thus rendering the acceptor less negatively charged. In some examples, the sulfotransferase is a glycosyl sulfotransferase, such as GST-O, GST-I , GST-2, GST-3, GST-4α, GST-4β, GST-5, or GST-6, or a heparin sulfate sulfotransferase, such as HS-NST, HS-2-OST, HS-3-OST, or HS-6-OST. Methods for separating a negatively charged acceptor from an acceptor with a more neutral charge (or having a neutral charge, that is, that is not charged), or having a less negative charge as compared to a negatively charged acceptor, based on charge differential are provided herein. Methods for separating a sulfated acceptor from a non-sulfated acceptor based on a charge differential are provided herein, wherein said non-sulfated acceptor has been combined with a sulfotransferase polypeptide and a sulfate donor in the presence of an agent and under conditions suitable to produce a sulfated acceptor. The presence of and/or amounts of non-sulfated acceptor and/or sulfated acceptor separated by charge can be detected or measured by methods known in the art. In some examples, an acceptor comprises a detectable label, such as a fluorophor. The present invention provides methods for determining whether an agent modulates the activity of a sulfotransferase polypeptide comprising separating non-sulfated acceptor from a sulfated acceptor based on a charge differential, wherein said non-sulfated acceptor has been combined with a sulfotransferase polypeptide and a sulfate donor in the presence of an agent and under conditions suitable to produce a sulfated acceptor, and optionally detecting and/or measuring the presence of a non-sulfated and/or sulfated acceptor separated as compared to an appropriate control or baseline value. In some examples, the methods include detecting and/or measuring the presence of a non-sulfated and/or sulfated acceptor separated as compared to an appropriate control or baseline value. In other examples, the present invention provides methods of ■ determining whether an agent modulates the activity of a sulfotransferase polypeptide comprising the steps of a) combining the sulfotransferase polypeptide with a sulfate donor; and an acceptor (which may comprise a detectable label) wherein said combining is under conditions suitable to produce a sulfated acceptor (which may comprise a detectable label), wherein the sulfated acceptor is negatively charged; b) separating negatively charged sulfated acceptor from said acceptor based on a charge differential, and optionally detecting the presence and/or amount of sulfated acceptor compound produced, which may be compared to an appropriate control or baseline value. In some examples, the acceptor combined with the sulfotransferase polypeptide is non-sulfated and in other examples has a neutral charge (that is, is not charged) or has a more neutral charge than the negatively charged sulfated acceptor. [0009] Methods for separating a sulfated acceptor from a non-sulfated acceptor based on a charge differential are provided herein, wherein said sulfated acceptor has been combined with a sulfatase polypeptide in the presence of an agent and under conditions suitable to release a sulfate moiety from the sulfated acceptor. The presence of and/or amounts of non-sulfated acceptor and/or sulfated acceptor separated by charge can be detected or measured by methods deemed routine to one of skill in the art. In some examples, an acceptor comprises a detectable label which can be detected and/or measured and compared to an appropriate control or baseline value. In some examples, the acceptor comprises a detectable label such as a fluorophor. The present invention provides methods for determining whether an agent modulates the activity of a sulfatase polypeptide comprising separating non-sulfated acceptor from a sulfated acceptor based on a charge differential, wherein said sulfated acceptor has been combined with a sulfatase polypeptide in the presence of an agent and under conditions suitable to release a sulfate moiety from the sulfated acceptor, and optionally detecting and/or measuring the presence of a non- sulfated and/or sulfated acceptor separated as compared to an appropriate control or baseline value. In some examples, the presence of a non-sulfated acceptor and/or sulfated acceptor is detected and/or measured. In other examples, the present invention provides methods of determining whether an agent modulates the activity of a sulfatase polypeptide comprising the steps of a) combining the sulfatase polypeptide with an appropriate sulfated acceptor (which may comprise a detectable label) and an agent to be tested, wherein said contacting is under conditions suitable to release a sulfate moiety from the sulfated acceptor and b) separating negatively charged sulfated acceptor from said acceptor having a more neutral charge or having a neutral charge (that is, that is not charged), and optionally detecting and/or measuring the amount of non-sulfated acceptor and/or sulfated acceptor produced, which may be compared to an appropriate control or baseline value. [0010] The present invention also provides sulfotransferase fragments and variants that are capable of transferring a sulfate moiety from a donor to an appropriate acceptor molecule as well as vectors, host cells and compositions comprising such fragments and variants. The present invention also provides complexes comprising a sulfotransferase polypeptide bound to an agent, complexes comprising a sulfatase polypeptide bound to an agent and compositions comprising such complexes.

BRIEF DESCRIPTION OF THE DRAWINGS [00111 FIGS. IA- I B are schematic diagrams depicting (IA) transfer of a sulfate moiety from a sulfate donor, 3'-phosphoadenosine-5-phosphosulfate (PAPS), to a sulfate acceptor comprising a fluorophore, GIcNAc labeled with coumarin (CmGIcNAc), catalyzed by glycosyltransferase-3 (GST-3) and (IB) separation of negatively charged sulfated CmGIcNAc from non-sulfated CmGIcNAc having a neutral charge. [0012) FIGS. 2A-2B show the reaction kinetics of a fluorescent-based assay as a function of (2A) CmGIcNAc and (2B) PAPS concentration. Figs. 2A-2B show the plot of rate as a function of (2A) CmGIcNAc and (2B) PAPS concentration for GST-3. [0013] FIGS. 3A-3B show the inhibition of GST-3 activity as measured using a fluorescent- based assay. FIG. 3 A depicts the % inhibition of GST-3 activity vs concentration of PAP; FIG. 3B depicts the % inhibition of GST-3 activity vs concentration of CoA. [0014] FIG. 4 shows the signal intensity versus background in the GST-O fluorescent assay after a 21 hour incubation with Lac-(9)-7DEACm as the substrate. [0015] FIG.5 shows the time course of GST-O activity using Lac-(9)-7DEACm as the substrate. DETAILED DESCRIPTION OF THE INVENTION [0016] A number of disease conditions have been associated with biological sulfation events such as for example acute or chronic inflammation associated with the binding of L-selectin to a sulfated glycoprotein ligand and tumor-induced angiogenesis. Enzymes involved in biological sulfation events include sulfotransferases, which catalyze the transfer of a sulfate moiety from a donor to an acceptor, and sulfatases, which release a sulfate from a substrate such as glycoprotein, sulfolipid, and proteoglycan: As the above enzymes are associated with biological sulfation events associated with disease conditions, there is a need for identifying agents that are capable of modulating the activity of these enzymes. [0017] The present invention relates to methods for screening for agents that modulate the activity of enzymes associated with sulfation of biological molecules, such as sulfotransferases, which catalyze the transfer of a sulfate moiety from a donor to an acceptor and sulfatases, which catalyze release of a sulfate moiety from an acceptor. Adding a sulfate moiety to an acceptor or releasing a sulfate moiety from an acceptor will increase or decrease the negative charge, respectively. The present invention provides cell free methods for determining whether an agent modulates the activity of an enzyme associated with sulfation comprising the step of separating a negatively charged acceptor from an acceptor with a more neutral charge (or having a neutral charge, that is, that is not charged) based on charge differential, and in some examples, includes methods for separating a non-sulfated acceptor from a sulfated acceptor based on charge differential. In some examples, the methods described herein are amenable to high-throughput screening of test agents. In some examples, the methods comprise combining a sulfotransferase polypeptide that catalyzes transfer of a sulfate moiety from a sulfate donor to an acceptor, with a sulfate donor; an acceptor (which may comprise a detectable label) and in some examples disclosed herein, comprises a fluorophor, wherein the acceptor (which may comprise a detectable label) has a charge that is more neutral than the sulfated acceptor; and a test agent. Any acceptor that becomes sulfated through the catalytic activity of the sulfotransferase polypeptide will have a more negative charge than the acceptor in the starting reaction and can be separated based on charge differential. In some examples, the acceptor in the starting reaction is non-sulfated and/or has a neutral charge (that is, is not charged). In other examples, the assay comprises contacting a sulfatase polypeptide that catalyzes release of a sulfate moiety from a sulfated acceptor, with a sulfated acceptor (that may comprise a detectable label) wherein said sulfated acceptor (that may comprises a detectable label) is negatively charged; and a test agent. Any sulfated acceptor that loses a sulfate moiety has a modification in charge and can be separated from the negatively charged sulfated acceptor, based on a charge differential. [0018] Materials useful for separating acceptors based on a charge differential include for example, anion exchange resins. The detection and/or quantitative measurement of sulfation of the acceptor can be determined by methods known by those of skill in the art, for example mass spectrometry, or by a measurement of a detectable label (which may be attached to the acceptor before or after separation), which in some illustrative examples is a fluorophor. [0019] Test agents which modulate, that is, enhance, inhibit or mimic the activity of an enzyme associated with sulfation, such as a sul fotransferase or sulfatase, may be readily identified using assays described herein. General Techniques [0020] The practice of the present invention will employ, unless otherwise indicated, conventional techniques of molecular biology (including recombinant techniques), cell biology, and biochemistry which are within the skill of the art. Such techniques are explained fully in the literature, such as, Molecular Cloning: A Laboratory Manual, second edition (Sambrook et al., 1989); Methods in Enzymology (Academic Press, Inc.); and Current Protocols in Molecular Biology (F. M. Ausubel et al., eds., 1987 and annual updates). [0021] As used herein the term, "sulfotransferase polypeptide" encompasses the full length sulfotransferase, as well as fragments thereof, such as catalytic fragments, variants thereof, and modified forms thereof, that are capable of transferring a sulfate group from a donor to an acceptor and includes sulfotransferase from any species. Sulfotransferase polypeptides (including fragments, variants, and modified forms) are functional as described above. GST-3 polypeptide as used herein encompasses the full length GST-3, as well as fragments thereof, such as catalytic fragments, variants thereof, and modified forms thereof, that are capable of transferring a sulfate group from a donor to an acceptor and includes GST-3 from any species. Modified forms of sulfotransferase polypeptides include sulfotransferases modified by disulfide bond formation, glycosylation, lipidation, and labeling components. [0022] As used herein, the term "sulfatase polypeptide" encompasses both the full length sulfatase, as well as fragments thereof, such as catalytic fragments, variants thereof, and modified forms thereof, that are capable of releasing a sulfate group from an acceptor and includes sulfatase from any species. Sulfatase polypeptides (including fragments, variants, and modified forms) are functional as described above. Modified forms of sulfatase polypeptides include sulfatases modified by disulfide bond formation, glycosylation, lipidation, and labeling components. [0023] "Modulate" as used herein with respect to the activity of a sulfotransferase, sulfotransferase polypeptide, sulfatase or sulfatase polypeptide refers to the ability of an agent to alter their activity including inhibiting, enhancing and mimicking the activity as compared to an appropriate control. "Activity" as used herein with respect to a sulfotransferase, sulfotransferase polypeptide, sulfatase or sulfatase polypeptide encompasses the catalytic activity. That is, a sulfotransferase or sulfotransferase polypeptide activity includes the capability of transferring a sulfate moiety from a donor to an appropriate acceptor and for a sulfatase polypeptide or sulfatase, activity includes the capability of releasing a sulfate (that is cleaving a sulfate) from an appropriate sulfated acceptor. As used herein, inhibition of activity does not require that the inhibition is complete or 100%. Inhibition may be about a 5%, about a 10%, about a 20%, about a 30%, about a 40%, about a 50%, about a 60%, about a 70%, about a 80%, about a 90%, about a 95% or more reduction of activity as compared to an appropriate control. [0024] As used herein, the step of "separating" does not require that the separation of sulfated acceptors from non-sulfated acceptors be complete or 100%. The separation could be about any of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% or more, as long as it is possible to determine whether an agent, that is, a test agent has modulated the activity of the enzyme used. Assay method [0025] The present invention provides compositions, methods, and kits for determining whether an agent modulates the activity of an enzyme associated with sulfation, such as for example, a sulfotransferase or sulfatase. In some examples, the enzyme is a sulfotransferase polypeptide and in other examples is a sulfatase polypeptide. In particular, the present invention provides cell free methods for determining whether an agent modulates the activity of an enzyme associated with sulfation comprising the step of separating a sulfated acceptor having a negative charge from an acceptor which is non-sulfated, or which has a more neutral charge, or which has a neutral charge. In some examples when the enzyme is a sulfotransferase polypeptide, the acceptor in the starting reaction is non-sulfated and has a neutral charge and any sulfated acceptor produced as a result of the action of the sulfotransferase polypeptide will have a negative charge and can be separated based on a charge differential. In some examples when the enzyme is a sulfatase polypeptide, the acceptor in the starting reaction is sulfated and has a negative charge and any acceptor produced as a result of the action of the sulfatase polypeptide will be non-sulfated and will have a more neutral charge or will have a neutral charge and can be separated based on a charge differential. Examples of acceptors are described herein. Following separation, the amount of negatively charge acceptor and/or acceptor having a more neutral charge and/or non-sulfated acceptor and/or sulfated acceptor can be compared to an appropriate control to determine the ability of an agent to modulate the activity of an enzyme. In some examples, the detection or measurement of separation of a non-sulfated acceptor from a sulfated acceptor is accomplished through methods deemed routine to the skilled artisan, such as for example, mass spectrometry. In others examples, the acceptor comprises a detectable marker which can be measured, detected, quantified and/or compared to a control or a baseline value. In other examples, after the separation, the ratio of non-sulfated' acceptor to sulfated acceptor can be measured. Accordingly, the present invention provides methods for comparing the amount of a sulfated acceptor (or amount of negative charged acceptor) to an acceptor that is non-sulfated (or to an acceptor that has a more neutral charge or has a neutral charge), comprising the steps of a) measuring the amount of sulfated acceptor (or amount of negative charged acceptor); b) measuring the amount of the acceptor that is non-sulfated (or amount of acceptor that has a more neutral charge or has a neutral charge) wherein the steps of a) and b) can be in any order; and c) comparing a) to b) to determine the ability of an agent to modulate the activity of the enzyme. Methods using an acceptor comprising a detectable label, such as for example, a fluorophor, facilitate high through-put screening methods. [0026] In some examples, the present invention provides methods for separating a non- sulfated acceptor from a sulfated acceptor based on a charge differential, wherein said non- sulfated acceptor has been combined with a sulfotransferase polypeptide and a sulfate donor in the presence of an agent and under conditions suitable to produce a sulfated acceptor. The presence of or amounts of non-sulfated acceptor and/or sulfated acceptor separated by charge can be detected or measured by methods routine to one of skill in the art. In some examples, an acceptor comprises a detectable label which can be measured and compared to an appropriate control or baseline value. In some examples, the acceptor comprises a detectable label such as a fluorophor. The present invention provides methods for determining whether an agent modulates the activity of a sulfotransferase polypeptide comprising separating a non-sulfated acceptor from a sulfated acceptor based on a charge differential, wherein said non-sulfated acceptor has been combined with a sulfotransferase polypeptide and a sulfate donor in the presence of an agent and under conditions suitable to produce a sulfated acceptor, and detecting and/or measuring the presence of a non-sulfated and/or sulfated acceptor separated as compared to an appropriate control or baseline value. In other examples, the present invention provides methods of determining whether an agent modulates the activity of a sulfotransferase polypeptide comprising the steps of a) combining the sulfotransferase polypeptide with a sulfate donor; an acceptor (which may comprise a detectable label) wherein the acceptor has a more neutral charge than the acceptor when it is sulfated; and an agent to be tested, wherein said contacting is under conditions suitable to produce a sulfated acceptor, wherein the sulfated acceptor is negatively charged; b) separating any negatively charged sulfated acceptor from said acceptor having a more neutral charge, and detecting the amount of sulfated acceptor compound produced and/or amount of acceptor having a more neutral charge. In some examples, the acceptor in step a) is non-sulfated or has a neutral charge (that is, is not charged). [0027J In other examples, the present invention provides methods for separating a non- sulfated acceptor from a sulfated acceptor based on a charge differential, wherein said sulfated acceptor has been combined with a sulfatase polypeptide in the presence of an agent and under conditions suitable to release a sulfate moiety from the sulfated acceptor. The sulfated acceptor acted upon by the sulfatase polypeptide will be non-sulfated or will have a more neutral charge or will have a neutral charge and the presence of and/or amount of acceptor that is non-sulfated or that has a more neutral charge or that has a neutral charge and/or sulfated acceptor separated by charge differential can be detected or measured by methods routine to one of skill in the art. In some examples, an acceptor comprises a detectable label which can be measured and compared to an appropriate control or baseline value. In some examples, the acceptor comprises a detectable label such as a fluorophor. The present invention provides methods for determining whether an agent modulates the activity of a sulfatase polypeptide comprising separating a non- sulfated acceptor from a sulfated acceptor based on a charge differential, wherein said sulfated acceptor has been combined with a sulfatase polypeptide in the presence of an agent and under conditions suitable to release a sulfate moiety from the sulfated acceptor, and detecting and/or measuring the presence of a non-sulfated and/or sulfated acceptor separated as compared to an appropriate control or baseline value. In other examples, the present invention provides methods of determining whether an agent modulates the activity of a sulfatase polypeptide comprising the steps of a) combining the sulfatase polypeptide with an appropriate sulfated acceptor, which is negatively charged and which may comprise a detectable marker, and an agent to be tested, wherein said contacting is under conditions suitable to release a sulfate moiety from the sulfated acceptor and b) separating any negatively charged sulfated acceptor from said acceptor acted upon by the sulfatase polypeptide, which may be non-sul fated or which may have a more neutral charge or which has a neutral charge (that is, which is not charged), and optionally detecting and/or measuring the amount of sulfated acceptor, having a negative charge, and/or acceptor having a more neutral charge or having a neutral charge, produced. [0028] As will be understood by one of skill in the art, a variety of controls may be used in the methods disclosed herein. In some examples, a parallel method is performed with a known modulator of the enzyme which serves as a control or baseline value. In other examples, a parallel method is performed in the absence of a test agent or enzyme which serves as a control or baseline value. Absolute values of sulfated and/or non-sulfated acceptors can be measured and compared to an appropriated control or ratios of non-sulfated acceptor to sulfated acceptor >are measured or ratios of negatively charged acceptor to acceptor having a more neutral charge (or having a neutral charge) are measured. For an agent being screened for its ability to enhance sulfotransferase activity, a higher ratio of sulfated acceptor to non-sulfated acceptor is desirable (that is, a higher ratio of negatively charged acceptor to acceptor having a more neutral charge or having a neutral charge is desirable) . For an agent being screened for its ability to enhance sulfatase activity, a higher ratio of non-sulfated acceptor to sulfated acceptor is desirable (that is, a higher ratio of neutral acceptor or more neutral acceptor to negatively charged acceptor is desirable). For an agent being screened for its ability to inhibit sulfotransferase activity, a higher ratio of non-sulfated acceptor to sulfated acceptor is desirable (that is, a higher ratio of acceptor having a more neutral charge or having a neutral charge to negatively charged acceptor is desirable) . For an agent being screened for its ability to inhibit sulfatase activity, a higher ratio of sulfated acceptor to acceptor having a more neutral charge or having a neutral charge is desirable (that is, a higher ratio of negatively charged acceptor to acceptor having a more neutral charge or having a neutral charge is desirable). The present invention also provides methods of determining whether an agent modulates the activity of a sulfotransferase polypeptide or sulfatase polypeptide comprising determining any of: a) determining the presence and/or amount of sulfated acceptor, having a negative charge, and/or acceptor having a more neutral charge which results from any reaction described herein; b) determining the amount of sulfated acceptor, having a negative charge, and/or acceptor having a more neutral charge which results from any reaction described herein as compared to an appropriate control or baseline; and c) determining the ratio of sulfated acceptor, having a negative charge, to acceptor having a more neutral charge which results from any reaction described herein. As is clear to one skilled in the art, such determinations can indicate modulation by an agent (or lack of modulation). Modulation by an agent can be inhibition of activity or enhancement of activity. [0029] In some examples, the present invention provides rapid and/or high-throughput and/or quantitative screening methods for detecting agents that inhibit, or enhance the activity of an enzyme associated with sulfation, such as for example, a sulfotransferase or sulfatase. The present invention provides methods for determining whether an agent modulates, such as inhibits or enhances, the activity of a sulfotransferase polypeptide. In some examples, the sulfotransferase is a glycosylsulfotransferase, such as GST-O, GST-I , GST-2, GST-3, GST-4α, GST-4β, GST-5, or GST-6, or a heparin sulfate sulfotransferase, such as HS-NST, HS-2-OST, HS-3-OST, or HS-6-OST. The present invention also provides methods for determining whether an agent modulates the activity of a sulfatase polypeptide. In some examples, the sulfatase is human sulfl or human sulf2 as disclosed in U.S. 2003/0147875. [0030] The methods of the present invention comprise a step of separating sulfated acceptors from non-sulfated acceptors based on charge. As used herein, the step of "separating" does not require that the separation of sulfated acceptors from non-sulfated acceptors be complete or 100%. The separation could be about any of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% or more as long as it is possible to determine whether a test agent has modulated the activity of the enzyme used. As described herein, various controls may be used in the methods of the present invention. Methods for separating molecules or compounds based on charge are known by one of skill in the art and include, for example, anion exchange resins such as for example, QAE Sephadex, Q Sepharose, DEAE Sepharose, DEAE Sephadex and the separation step may be performed in liquid phase or solid phase, such as on beads, or gels, or membranes or the like. In some examples, an anion exchange resin is selected that is capable of separating a sulfated acceptor from a non-sulfated acceptor based on a single charge. In some illustrative examples of the methods disclosed herein, multi-well plates comprising membranes with an anion exchange resin deposited therein are used, which system is amenable to robotic implementation and provides for rapid, high-throughput screening of test agents. [0031] A variety of other reagents may be included in the screening assay. These include reagents like salts, neutral proteins, e.g. albumin, detergents, etc that are used to facilitate optimal protein-protein binding and/or reduce non-specific or background interactions. Reagents that improve the efficiency of the assay, such as protease inhibitors, nuclease inhibitors, anti-microbial agents, etc. may be used. The above screening methods may be designed a number of different ways, where a variety of assay configurations and protocols may be employed, as are known in the art. For example, one of the components may be bound to a solid support, and the remaining components contacted with the support bound component. The above components of the method may be combined at substantially the same time or at different times. Incubations are performed at any suitable temperature, typically between 4° and 40° C. Incubation periods are selected for optimum activity, but may also be optimized to facilitate rapid high-throughput screening. Typically between 0.1 and 1 hours will be sufficient. Following the combining steps, the subject methods may further include a washing step to remove unbound components, where such a washing step is generally employed when required to remove label that would give rise to a background signal during detection, such as fluorescently labeled non-specifically bound components. [00321 A variety of different candidate agents may be screened by the above methods. Candidate agents encompass numerous inorganic and organic chemical classes, though typically they are organic molecules, preferably small organic compounds having a molecular weight of more than 50 and less than about 2,500 Daltons. Candidate agents comprise functional groups necessary for structural interaction with proteins, particularly hydrogen bonding, and typically include at least an amine, carbonyl, hydroxyl or carboxyl group, preferably at least two of the functional chemical groups. The candidate agents often comprise cyclical carbon or heterocyclic structures and/or aromatic or polyaromatic structures substituted with one or more of the above functional groups. Candidate agents are also found among biomolecules including proteins, polypeptide, peptides, saccharides, fatty acids, steroids, purines, pyrimidines, derivatives, structural analogs, polynucleotides or combinations thereof. Antibodies include antibodies such as monoclonal and polyclonal antibodies, as well as fragments thereof. [0033] Candidate agents are obtained from a wide variety of sources including libraries of synthetic or natural compounds. For example, numerous means are available for random and directed synthesis of a wide variety of organic compounds and biomolecules, including expression of randomized oligonucleotides and oligopeptides. Alternatively, libraries of natural compounds in the form of bacterial, fungal, plant and animal extracts are available or readily produced. Additionally, natural or synthetically produced libraries and compounds are readily modified through conventional chemical, physical and biochemical means, and may be used to produce combinatorial libraries. Known pharmacological agents may be subjected to directed or random chemical modifications, such as acylation, alkylation, esterification, amidification, etc. to produce structural analogs. [0034] Without being bound by theory, test agents that are determined to inhibit transfer of a sulfate moiety from donor to acceptor in an assay method of the present invention may be binding the sulfo transferase, or fragment thereof, thereby creating a complex comprising the sulfotransferase, or fragment thereof, and test agent. Accordingly, the present invention provides complexes comprising a sulfotransferase polypeptide and compositions comprising such complexes. In some examples, the sulfotransferase is a glycosylsulfotransferase such as for example, GST-O, GST-I, GST-2, GST-3, GST-4α, GST-4β, GST-5, or GST-6, or a heparin sulfate sulfotransferase, such as HS-NST, HS-2-OST, HS-3-OST, or HS-6-OST. In other examples, a test agent is a small organic molecule, synthetic carbohydrate or peptide mimic. In some examples, the complex comprises a GST-3 polypeptide bound to a small molecule. Accordingly, the present invention provides a complex comprising a GST-3 fragment consisting of the amino acid sequence from about amino acid residue 30 to about amino acid residue 386 of SEQ ID NO:1 bound to a test agent. A complex may comprise any of the GST-3 fragments disclosed herein. The in vitro results of binding of an enzyme associated with a sulfation pathway, such as a sulfotransferase, with a test agent, such as a small molecule, are predicted to simulate in vivo activity. Without being bound by theory, test agents that are determined to inhibit release of a sulfate moiety from an acceptor in an assay method of the present invention may be binding the sulfatase, or fragment thereof. Accordingly the present invention provides complexes comprising a sulfatase polypeptide and compositions comprising such test agents. In some examples, a test agent is a small organic molecule. The present invention also comprises compositions comprising a complex comprising a sulfotransferase polypeptide bound to a test agent, as well as compositions comprising a sulfatase polypeptide bound to a test agent. [0035] In an illustrative example as shown schematically in Figs 1 A-IB, an assay comprises the steps of contacting a sulfotransferase (GST-3) or a fragment thereof that is capable of transferring a sulfate moiety from a donor to an acceptor, with PAPS and a synthetic carbohydrate acceptor molecule. Included in the assay is an agent to be tested, such as a small molecule. The contacting of these components is performed under conditions suitable to produce a sulfated acceptor compound, wherein said sulfated acceptor molecule is negatively charged. Any sulfated acceptor molecules or compounds produced can be separated from any non-sulfated acceptor molecules or compounds using a material capable of binding negatively charged acceptor molecules or compounds and/or capable of binding a singly charged compound, such as a strong anion exchange resin. The amount of sulfated acceptor molecule can be determined by measuring the level of labeled acceptor molecule thus separated from the reaction. The detection step can be performed while the sulfated acceptor is bound to the anion exchange resin or the sulfated acceptor can be eluted from the resin and then detected. As shown in Figs. IA-I B, GST-3 catalyzes the transfer of a sulfuryl group from PAPS to the 6- hydroxyl of a terminal GIcNAc residue in a synthetic glycoconjugate. [0036] As described in Example 2, GST-3 was incubated with the sulfate donor PAPS and a fluorescent derivative of GIcNAc, that is, GIcNAc linked to a fluorescent coumarin moiety via a short ethanolamine linker (designated CmGIcNAc). The ability of the fluorescent derivative of GIcNAc to serve as a substrate for GST-3 was validated by incubating the fluorescent derivative of GIcNAc and GST-3 in the presence of radioactively labeled-PAPS and measuring the incorporation of 35S-labeled sulfate in GIcNAc by thin layer chromatography. The Km of the substrate for the enzyme was determined by the thin layer chromatography (TLC) assay to be in the range of 32-57 μM. When the fluorescent derivative of GIcNAc which had been labeled with radioactive 3:>S-sulfate through the action of GSTí3 was applied to an anion exchange resin, the radioactivity was found bound to the resin with no significant radioactivity detected in the eluent. [0037] To further validate the fluorescent assay, Michealis constants were determined after binding the sulfated fluorescent derivative of GIcNAc (CmGIcNAc) to anion exchange resin. As shown in Figs. 2A-2B, which depict the rate of reaction as a function of concentration of CmGIcNAc and PAPS, the Km values that were obtained were highly consistent with the values obtained previously with the radioactive assay. The K111 for CmGIcNAc was found to be about 25 to about 48 μM and about 2 to about 3 μM for PAPS. See Verdugo et al., Anal. Biochem. 2002, 307:330-336. Example 4 describes an activity assay for GST-O that uses a lactose acceptor substrate. [0038] Assays of the present invention disclosed herein are amenable to high throughput methods. For high throughput screening applications, reaction components and test agents can be robotically deposited into, for example, multi-well plates. After the reaction is allowed to occur, the reaction mixture can be robotically transferred from the multi-well plates and deposited onto anion chromatography resin contained within the wells of multi-well filter plate or other apparatus. Sulfated acceptor will be retained on the anion exchange resin by virtue of its negative charge while the neutral non-sulfated acceptor molecules will flow through the resin. For methods for detecting agents that modulate sulfotransferases or sulfatases, the sulfated acceptor bound to the resin can be read directly or alternatively, the sulfated acceptor can be eluted using an appropriate buffer and read on a fluorescent plate reader. Accordingly, the present invention provides systems for performing the methods described herein. The systems may comprise, in addition to the sulfotransferase polypeptides and/or sulfatase polypeptides and appropriate agents, multiwell plates, a chromatography component, and in some examples, a detection and/or measurement device (such as a fluorescent plate reader). Other components useful for such a system are described herein, and any one or more of these components may be included in the systems of the invention. [0039] The present invention also provides kits that comprise components necessary to perform assays of the present invention, that is, the screening methods can be provided as part of a kit. Thus, the invention further provides kits for detecting agents that modulate the activity of a sulfotransferase or sulfatase which may include synthetic acceptor molecules, sulfate donor molecules, a sulfotransferase polypeptide, such as a GST-3 polypeptide disclosed herein, and/or a sulfatase polypeptide and suitable buffers and instructions for performing the methods of the present invention. Procedures using these kits can be performed by clinical laboratories, experimental laboratories, medical practitioners, or private individuals. Accordingly, the present invention provides kits that comprise i) a sulfotransferase polypeptide, and ii) an acceptor (which may comprise a detectable marker), wherein said acceptor has a neutral charge. The present invention also provides kits that comprise i) a sulfatase polypeptide and ii) a sulfated acceptor molecule. Accordingly, the present invention provides kits for determining whether an agent modulates the activity of a GST-3 polypeptide comprising, i) a GST-3 fragment of less than about 360 amino acids in length comprising the amino acid sequence from about amino acid residue 37 (lysine) to amino acid residue 386 (histidine) of SEQ ID NO:1; and ii) an acceptor, optionally comprising a detectable label. Kits of the present invention may also include PAPS as the sulfate donor. Kits of the present invention may also include anion exchange resins, buffers, or any other materials necessary to perform the methods of the present invention, such as suitable instructions. [0040] The methods described herein may be implemented using any device capable of implementing the methods. Examples of devices that may be used include but are not limited to electronic computational devices, including computers of all types. When the methods described herein are implemented in a computer, the computer program that may be used to configure the computer to carry out the steps of the methods may be contained in any computer readable medium capable of containing the computer program. Examples of computer readable medium that may be used include but are not limited to diskettes, CD-ROMs, DVDs, ROM, RAM, and other memory and computer storage devices. The computer program that may be used to configure the computer to carry out the steps of the methods may also be provided over an electronic network, for example, over the internet, world wide web, an intranet, or other network. [0041] In one example, the methods described herein may be implemented in a system comprising a processor and a computer readable medium that includes program code means for causing the system to carry out the steps of the methods described in this patent. The processor may be any processor capable of carrying out the operations needed for implementation of the methods. The program code means may be any code that when implemented in the system can cause the system to carry out the steps of the methods described in this patent. Examples of program code means include but are not limited to instructions to carry out the methods described herein written in a high level computer language such as C++, Java, or Fortran; instructions to carry out the methods described herein written in a low level* computer language such as assembly language; or instructions to carry out the methods described herein in a computer executable form such as compiled and linked machine language. Enzymes associated with sulfation I. Sulfotransferases [0042] Sulfotransferases catalyze the transfer of a sulfate moiety from an activated donor to an acceptor, usually placing the sulfate moiety at a specific location on the acceptor, including for example, the hydroxyl or amino group of an acceptor. As used herein the term, "sulfotransferase polypeptide" encompasses the full length sulfotransferase, as well as fragments thereof, such as catalytic fragments, and variants thereof, and modifications thereof, that are capable of transferring a sulfate group from a donor to an acceptor and includes sulfotransferase from any species. The present invention provides methods for determining whether an agent, e.g. a test agent, modulates the activity of a sulfotransferase polypeptide. As used herein the term "modulate" encompasses enhancing the ability of a sulfotransferase polypeptide to transfer a sulfate moiety from a donor to an acceptor; and inhibiting the ability of a sulfotransferase polypeptide to transfer a sulfate moiety from a donor to an acceptor. Acceptor molecules for use in a sulfotransferase assay may be biological molecules, synthetic molecules mimicking a biological molecule or structure, such as synthetic carbohydrates, or nucleophiles (such as a phenolic compound) capable of accepting sulfate. In some examples, the nucleotide analogue 3- phosphoadenosine-5-phosphosulfate (PAPS) is the activated sulfate donor. [0043] There are a variety of different sulfotransferases which vary in activity, i.e. with respect to the donor and/or acceptor compounds with which they work. Known sulfotransferases include those that catalyze the transfer of a sulfate moiety from a donor to a carbohydrate, such as for example, heparin/heparin sulfate N-sulfotransferases (NST); chondroitin 6/keratin 6 sulfate sulfotransferases (C6ST/KSST); and galactose/GalNac/GlcNAc 6-0 sulfotransferases as well as sulfotransferases that catalyze the transfer of a sulfate moiety from a donor to a phenol, steroid and xenobiotic. Many mammalian sulfotransferases have been identified and include the following: cytosolic sulfotransferases, including liver estrogen sulfotransferases disclosed in U.S. Pat. No. 5,744,355 and U.S. Pat. No. 6,265,561, neural tissue cytosolic sulfotransferase, disclosed in PCT publication WO/0218541 , and aryl sulfotransferase disclosed in PCT publication WO/0138581 ; tyrosyl sulfotransferases such as those disclosed in Moore KL (2003), J Biol Chcm 278:24243; Kehoe, J. W. et al. 2000, Chem. Biol., 7, R57-R61 ; Kehoe, J. W. et al. 2002, Bioorg. Med. Chem. Lett., 12, 329-332; Ouyang, Y. B et al. 1998, Proc. Natl. Acad. Sci. U.S.A., 95: 2896-2901 ; and Beisswanger, R. et al. 1998, Proc. Natl. Acad. Sci. U.S.A., 1998. 95: 1 1 134-1 1139. galNAc-4-O-sulfotransferase such as that disclosed in U.S. Pat. No. 6,323,332, and chondroitin-4-sulfotransferases such as those disclosed in U.S. Pat. No. 6,372,466; GaINAc- 4-sulfate 6-O-sulfotransferase, including the enzyme disclosed in PCT publication WO/0233097; galactose 3-O-sulfotransferases, including ceramide-3-sulfotransferase and gal -3- ST such as those disclosed in Honke K. et al (1997) J Biol Chem. 272:4864-8; Honke K. et al. (2001) J Biol Chem 276:267-74; Suzuki A. et al. (2001) J Biol Chem. 276:24388-95; Seko A. et al. J Biol Chem 276:25697-704. heparan sulfate sulfotransferases, including heparin sulfate N-sulfotransferase (HS-NST), disclosed in for example, Kjellen L. (2003) Biochem Soc Trans. 31 :340-2; HS-2- OST disclosed in U.S. Pat. No. 5,817,487 and Rong J. et al. Biochem J 346:463-8; HS-3-OST disclosed in Shworak NW. (1999) J Biol Chem 274:5170-84; HS-6-OST disclosed in for example U.S. Pat. No. 5,834,282 and Habuchi H. 1998, J Biol Chem 273:9208-13 and Habuchi H. et al., 2000, J Biol Chem 275:2859-68; and dermatan sulfate 2-O-ST disclosed in Kobayashi M. et al., 1999, J Biol Chem. 274: 10474-80; and galactose/GalNAc/GlcNAc 6-O-sulfotransferases (ST) which include Galactose 6-O-ST, glycosylsulfotransferase-0 (GST-O) disclosed in U.S. Pat. Nos. 5,910,581 and 5,827,713; GST-I disclosed in U.S. Pat. Nos. 6,051 ,406 and 6,399,358; GIcNAc 6-OST including GST-2 disclosed in U.S. Pat. No. 6,037,159; GST-3 disclosed in U.S. Pat. No. 6,265,192; GST 4α and 4β disclosed in PCT publication WO 01/06015; GST-5 disclosed in Bhakta et al. 2000, J. of Biol. Chem, 275:40226, and GST-6, disclosed in PCT publication WO 01/06015. The disclosures of the above patent publications are specifically incorporated herein by reference in their entirety. [0044) The present invention also provides fragments of sulfotransferases, such as fragments of GSTs, that have the ability to catalyze the transfer of a sulfate moiety from a donor to an appropriate acceptor. Such fragments are referred to herein as "catalytic fragments". Fragments of interest will be at least about 50 amino acids in length, about 75 amino acids in length, about 100 amino acids in length, about 150 amino acids in length, about 200 amino acids in length, about 250 amino acids in length, or about 300 amino acids in length or longer. Fragments of interest will be less than about 400 amino acids in length, less than about 350 amino acids in length, less than about 300 amino acids in length, less than about 250 amino acids in length, less > than about 200 amino acids in length, or less than about 150 amino acids in length. GST fragments are disclosed herein. The present invention also encompasses sulfotransferase "variants", such as GST "variants" that is, sulfotransferase or GST amino acid sequences comprising amino acid substitutions, additions and/or deletions that retain the ability to catalyze the transfer of a sulfate moiety from an appropriate donor to an appropriate acceptor. Such sulfotransferase variants, such as GST-3 variants, will have at least about 60%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% identity or greater to the naturally occurring sulfotransferase as measured using software programs known in the art, for example those described in Current Protocols in Molecular Biology (F. M. Ausubel et al., eds., 1987) Supplement 30, section 7.7.18. A preferred alignment program is ALIGN Plus (Scientific and Educational Software, Pennsylvania), preferably using default parameters, which are as follows: mismatch = 2; open gap = 0; extend gap = 2. A GST-3 variant will have at least about 60%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% identity to the GST-3 sequence disclosed in Example 5 (SEQ ID NO: 1). A GST-2 variant will have at least about 60%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% identity to the GST-2 sequence disclosed in Example 6 (SEQ ID NO: 2). [0045] The present invention also encompasses nucleic acid encoding such sulfotransferase fragments and variants (such as GST-3 fragments and variants) and vectors, host cells and compositions comprising them. Readily-available functional assays deemed routine to the skilled artisan, and assays such as those disclosed herein, will allow one of ordinary skill to determine whether a sulfotransferase fragment or variant such as a GST fragment or variant, retains the ability to catalyze the transfer of a sulfate moiety from a donor to an appropriate acceptor, that is, retains catalytic activity. Nucleic acid and polynucleotides are used interchangeable herein. In some examples, the polynucleotide is DNA. As used herein, "DNA" includes not only bases A, T, C, and G, but also includes any of their analogs or modified forms of these bases, such as methylated nucleotides, internucleotide modifications such as uncharged linkages and thioates, use of sugar analogs, and modified and/or alternative backbone structures, such as polyamides. [0046] A table providing the systematic names and commonly used designations of the family of GlcNAc-6-o-sulfotransferases is provided in Lee et al. (2003, Glycobiology, vol. 13:245-254) and is provided below as Table I.. ■ ■ Table I Systematic name Other designations GlcNAc6ST-l GlcNAcόST, GST-2*, CHST-2 GlcNAc6ST-2 HEC-GlcNAc6ST, LSST, GST-3, CHST4 GlcNAc6ST-3 I-GlcNAc6ST, GST-4α, CHST5 GlcNac6ST-4 C6ST-2, GST-5, CHST7 GlcNAc6ST-5 C-GIcN AcόST, GST-4β, CHST6 *GST is the designation for glycosylsulfotransferase [0047] The methods of the present invention encompass the use of any sulfotransferase polypeptide, provided that the appropriate acceptor is selected for use with the particular sulfotransferase polypeptide. Particular sulfotransferases and their in vivo and/or in vitro sulfate acceptor molecules are disclosed herein. In some examples, a sulfotransferase is a mammalian sulfotransferase. As used herein, the term "mammalian" encompasses primates, such as humans; rodents, such as murine; farm animals, such as bovine and ovine; and sports animal, such as equine. |0048| In some examples, the sulfotransferase polypeptide is a glycosylsulfotransferase, such as mammalian GST-O, GST-I , GST-2, GST-3, GST-4α, GST-4β, GST-5 or GST-6 or a variant thereof or fragment thereof that is capable of catalyzing the transfer of a sulfate moiety from a donor to an acceptor. In other examples, the sulfotransferase is GST-O, or a variant thereof or a fragment thereof that is capable of catalyzing the transfer of a sulfate moiety from a donor to an acceptor. In yet other examples, the sulfotransferase is GST-I , or a variant thereof or a fragment thereof that is capable of catalyzing the transfer of a sulfate moiety from a donor to an acceptor. In further examples, the sulfotransferase is GST-2, or a variant thereof or a fragment thereof that is capable of catalyzing the transfer of a sulfate moiety from a donor to an acceptor. In other examples, the sulfotransferase is GST-3, or a variant thereof or a fragment thereof that is capable of catalyzing the transfer of a sulfate moiety from a donor to an acceptor. The present invention provides GST-2 and GST-3 fragments that have catalytic activity. In addition, the present invention provides GST-3 variants that have catalytic activity. In one illustrative embodiment disclosed herein, the present invention provides a GST-3 variant that comprises a substitution of the amino acid residue 329 N (Asn) with Q (GIn) (referred to herein as N329Q). [00491 In other examples, the sulfotransferase is GST-4α, or a variant thereof or a fragment thereof that is capable of catalyzing the transfer of a sulfate moiety from a donor to an acceptor. In other examples, the sulfotransferase is GST-4β, or a variant thereof or a fragment thereof that is capable of catalyzing the transfer of a sulfate moiety from a donor to an acceptor. In other examples, the sulfotransferase is GST-6, or a variant thereof or a fragment thereof that is capable of catalyzing the transfer of a sulfate moiety from a donor to an acceptor. [0050| In yet other examples, the sulfotransferase is a heparin sulfate sulfotransferase, such as mammalian HS-NST, HS-2-OST, HS-3-OST, HS-6-OST or dermatan sulfate 2-O-ST or a variant thereof or fragment thereof that is capable of catalyzing the transfer of a sulfate moiety from a donor to an acceptor. [0051] A sulfotransferase (ST) employed in an assay of the present invention may be produced by methods well known to those of skill in the art. The ST, or fragment thereof, may be isolated from a biological sample, or produced by recombinant methods, or isolated from genetically engineered cells that produce the ST. As used herein, the term "isolated" means that the ST is removed from at least one component with which it is naturally associated. The present invention encompasses the use of ST present in an extract containing ST activity. Examples of extracts that can be used in sulfotransferase assays are disclosed in the literature. For example, To et al. (1984, J. Chromatography, vol. 301 :282-287), Honkasalo et al. (1988, J Chromatography vol. 424:136-40), and Sim et al. (1990, J. Pharmacol. Methods vol. 24:157-63) disclose the use of extracts containing ST activity derived by the homogenization of various rat tissues, including brain and liver. In a disclosure, the resulting homogenate was centrifuged at 100,000 x g for 60 minutes at 0°C to obtain the final extract used in assays. To et al., supra, disclose that a homogenate prepared in this manner can be used at a concentration of about 1 to about 5 mg/ml in a sulfotransferase assay. [0052] The present invention also encompasses the use of fragments of sulfotransferases that are capable of transferring a sulfate moiety from a donor to an acceptor, referred to herein as "catalytic fragments". The GIcNAc 6-0 sulfotransferase, GST-3, is expressed in high endothelial cells (HEC) and is associated with sulfation of selectin ligands associated with selectin mediated binding events, such as those involved in immune surveillance. In some examples, the present invention encompasses the use of GST-3 fragments, that are capable of transferring a sulfate moiety from a donor, e.g. PAPS, to an acceptor, such as glycoproteins with predominantly N-linked chains and mucin type acceptors. See Lee et al., supra. [0053] In some examples, the present invention provides GST-3 catalytic fragments. The amino acid sequence of GST-3 is disclosed in U.S. Patent No. 6,265,192, Figure 2 and SEQ ID NO:02, specifically incorporated herein by reference in its entirety, and is disclosed herein in the examples. As disclosed herein in the Examples, a fragment of GST-3 as shown in Figure 2 of U.S. Patent No. 6,265,192, from amino acid residue 30 (asparagine) to the last amino acid residue in the protein, histidine 386, is active in the assay described herein in Example 2. A fragment of GST-3 as shown in Figure 2 of U.S. Patent No. 6,265,192 from amino acid residue 37 (lysine) to the last amino acid residue in the protein, histidine 386, has reduced activity in the assay described herein in Example 2. A fragment of GST-3 as shown in Figure 2 of U.S. Patent No. 6,265,192 from amino acid residue 44 (histidine) to the last amino acid residue in the protein, histidine 386, is inactive in the assay described herein in Example 2. Accordingly, the present invention provides GST-3 fragments that are capable of transferring a sulfate moiety from a donor to an acceptor and vectors, host cells and compositions and kits comprising such fragments. Such GST-3 fragments comprise a deletion of N-terminal amino acid residues of GST-3 as shown in Figure 2 of U.S. Patent No. 6,265,192 from about amino acid residue 30 (asparagine) to about amino acid residue 37 (lysine). That is, a GST-3 catalytic fragment can comprise a deletion of about the first 30 N-terminal amino acid residues, about the first 31 N- terminal amino acid residues, about the first 32 N-terminal amino acid residues, about the first 33 N-terminal amino acid residues, about the first 34 N-terminal amino acid residues, about the first 35 N-terminal amino acid residues, about the first 36 N-terminal amino acid residues, or about the first 37 N-terminal amino acid residues of the GST-3 as shown in Figure 2 of U.S. Patent No. 6,265,192 and still retain activity in the assay as described in Example 2. Such GST- 3 fragments can be used in any assay for measuring GST-3 activity. The present invention encompasses GST-3 variants that are capable of transferring a sulfate moiety from a donor to an acceptor in any assay for measuring GST-3 activity. In one illustrative embodiment, a GST-3 variant is GST-3 N329Q. Accordingly, the present invention provides N329Q and compositions comprising N329Q for use in any assay that requires GST-3 activity. Accordingly, the present invention encompasses GST-3 fragments of less than about 380 amino acids in length, less than about 375 amino acids in length, less than about 370 amino acids in length, less than about 365 amino acids in length, less than about 360 amino acids in length, less than about 355 amino acids in length, or less than about 350 amino acids in length and in some examples, about 356 amino acids in length, or about 355 amino acids in length, or about 354 amino acids in length, or about 353 amino acids in length or about 352 amino acids in length, or about 351 amino acids in length or about 350 amino acids in length or about 349 amino acids in length comprising an amino acid sequence having about 85% identity to the amino acid sequence from about amino acid residue 37 (lysine) to about amino acid residue 386 (histidine) of SEQ ID NO: 1 , wherein said fragment is capable of transferring a sulfate moiety from a sulfate donor to an acceptor. The present invention encompasses GST-3 fragments of less than about 380 amino acids in length, less than about 375 amino acids in length, less than about 370 amino acids in length, less than about 365 amino acids in length, less than about 360 amino acids in length, less than about 355 amino acids in length, or less than about 350 amino acids in length and in some examples, about 356 amino acids in length, or about 355 amino acids in length, or about 354 amino acids in length, or about 353 amino acids in length or about 352 amino acids in length, or about 351 amino acids in length or about 350 amino acids in length or about 349 amino acids in length comprising the amino acid sequence from about amino acid residue 37 (lysine) to about amino acid residue 386 (histidine) of SEQ ID NO.l, wherein said fragment is capable of transferring a sulfate moiety from a sulfate donor to an acceptor. In some examples, the GST-3 fragment is from about amino acid residue 30 (asparagine) to about amino acid residue 386 (histidine) of SEQ ID NO: 1, wherein said fragment is capable of transferring a sulfate moiety from a sulfate donor to an acceptor. The present invention comprises compositions comprising such fragments. [0054] In other examples, the present invention provides GST-2 catalytic fragments. The amino acid sequence of GST-2 is disclosed in GenBank number NP 004258 (specifically incorporated herein by reference) and is provided in the Examples. As disclosed herein, a fragment of GST-2 from amino acid residue D75 to amino acid residue L530 had catalytic activity in the assay described in Example 2. Accordingly, the present invention provides GST- 2 fragments that are capable of transferring a sulfate moiety from a donor to an acceptor and compositions and kits comprising such fragments. [0055] In another example, the present invention encompasses the use of fragments of human GST-4α that are capable of transferring a sulfate moiety from a donor to an acceptor, such as O-linked sugars of mucin-type acceptors. See Lee et al., supra. The amino acid sequence for GST-4α is disclosed in PCT publication WO 01/06015, Figure 1 and SEQ ID NO:08, specifically incorporated herein by reference in its entirety. The present invention encompasses the use of fragments of GST-4α that are capable of transferring a sulfate moiety from a donor to an acceptor and compositions comprising such fragments of GST-4α in an assay that requires GST-4α catalytic activity. [0056] In another example, the present invention encompasses the use of fragments of human GST-4β that are capable of transferring a sulfate moiety from a donor to an acceptor molecules. Known acceptor molecules of GST-4β include keratin sulfate proteoglycans and mucin-type glycoproteins including L-selectin ligands. The amino acid sequence for GST-4β is disclosed in PCT publication WO 01/06015, Figure 4B, SEQ ID NO: 13, specifically incorporated herein by reference in its entirety. The present invention encompasses the use of fragments of GST-4β that are capable of transferring a sulfate moiety from a donor to an acceptor and compositions comprising such fragments of GST-4β in an assay that requires GST- 4β catalytic activity. [0057] In another example, the present invention encompasses the use of fragments of human GST-6 that are capable of transferring a sulfate moiety from a donor to an acceptor. The amino acid sequence for GST-6 is disclosed in PCT publication WO 01/06015, Figure 3, SEQ ID NO:09, specifically incorporated herein by reference in its entirety. The present invention encompasses the use of fragments of GST-6 that are capable of transferring a sulfate moiety from a donor to an acceptor and compositions comprising such fragments of GST-6 in an assay that requires GST-6 catalytic activity. [0058] Additional fragments of sulfotransferases for use in the methods of the present invention can be determined by those of skill in the art by employing routine assays that detect transfer of a sulfate moiety from a donor molecule, such as PAPS, to an acceptor molecule. In particular, Grunwell et al., 2002, Biochemistry, vol. 41 :131 17-13126, disclose in Figure 2 an alignment of GSTs, specifically incorporated herein by reference in its entirety. The putative GST transmembrane domains are underlined in Figure 2 and shown below. For the GSTs listed in the Figure, that is, for GST-O, GST-I , GST-2, GST-3, GST-4α, GST-4β, and GST-6, fragments starting with the first amino acid residue after the transmembrane domain of each GST are predicted to retain catalytic activity. That is, for GST-O, GST-I , GST-2, GST-3, GST- 4α, GST-4β, and GST-6, fragments having a deletion of the N-terminal amino acids through the transmembrane domain are predicted to retain catalytic activity. GST-O YALFLVFVVIVFVFIEKENKIISRVSDKLKQIPQALADANSTDPALILAENASLLSLSEL DSAFS GST-I AVLLLALASIAIQYT AIRTFTAKSFHTCPGLAEAG GST-2 ALVLCAGYALLLVLTMLNLLDYKWHKEPLQQCNPDGPLGAAAGAAGGSWGRPGPPPAGPP RAHARL GST-3 LLLFLVSQMAILALFFHMYSHNIS GST-4α CTVTVLLLAQTTCLLLFIISR GST-4β AVTALLAQT-FLLLFLVSR GST-5 ALLLVLYTLVLLLVPSVL DGGRDGDKGAEHCPGLQRSLGVWSLE

II. Sulfatases [0059] Sulfatase enzymes catalyze the hydrolysis of sulfate ester bonds from a wide variety of substrates ranging from complex molecules such as glycosaminoglycans and sulfolipids to steroid sulfates and are associated with a variety of physiological processes, including development, metabolism, and inflammation as well as disease conditions. Desulfation is required to degrade glycosaminoglycans, heparan sulfate, chondroitin sulfate and dermatan sulfate and sulfolipids. The sulfatase gene family has been reviewed in Parenti et al. (1997, Current Opinion in Genetics and Development 7:386-391. As used herein, the term "sulfatase polypeptide" encompasses both the full length sulfatase, as well as fragments thereof, such as catalytic fragments, and variants thereof, that are capable of releasing a sulfate group from an acceptor and includes sulfatase from any species. The present invention provides methods for determining whether an agent, e.g. a test agent, modulates the activity of a sulfatase polypeptide. As used herein the term "modulate" encompasses enhancing the ability of a sulfatase polypeptide to release a sulfate moiety from an acceptor; and inhibiting the ability of a sulfatase polypeptide to release a sulfate moiety from an acceptor. [0060] The natural substrates of iduronate-2-sulfate sulfatase (IDS) are dermatan sulfate and herparan sulfate. The natural substrate of galactose 6-sulfatase is keratan sulfate and chondroitin 6-sulfate. The natural substrate of glucosamine-6-sulfatase is heparan sulfate and keratan sulfate. The natural substrate of glucuronate-2-sulfatase is heparan sulfate. The natural substrate of glucosamine-3-sulfatase is heparan sulfate. Sulfatases associated with angiogenesis are disclosed in U.S. patent application publication U.S. 2003/0147875, specifically incorporated herein by reference in its entirety, and are designated as sulfl and sulf2. Human sulfl is disclosed in Fig. IB of U.S. 2003/0147875; murine sulfl is disclosed in Fig. 3B of U.S. 2003/0147875; human sulG is disclosed in Fig. 2B of U.S. 2003/0147875; and murine sulf2 is disclosed in Fig. 4B of U.S. 2003/0147875, specifically incorporated herein by reference in its entirety. As disclosed in U.S. 2003/0147857, the mammalian sulfl or sulf2 cleave (release) the sulfate moiety from N-acetylglucosamine-6-sulfate or glucosamine-6-sulfate structures within heparan sulfate glycosaminoglycans and related glycoconjugates. Acceptor molecules for use in a sulfatase assay may be biological molecules, synthetic molecules mimicking a biological molecule or structure, and/or synthetic carbohydrates, or sulfated fluorophores capable of releasing sulfate. Synthetic acceptor molecules can be designed based on naturally occurring sulfatase substrates. [00611 The present invention encompasses fragments of sulfatases that have the ability to release a sulfate moiety from an acceptor, such as a sulfated acceptor. Such fragments are referred to herein as "catalytic fragments". Fragments of interest will be at least about 50 amino acids in length, about 75 amino acids in length, about 100 amino acids in length, about 150 amino acids in length, about 200 amino acids in length, about 250 amino acids in length, about 300 amino acids in length, about 320 amino acids in length, about 340 amino acids in length, or about 350 amino acids in length or longer. The present invention also encompasses sulfatase "variants" that is, sulfatase amino acid sequences comprising amino acid substitutions, additions and/or deletions that retain the ability to release a sulfate moiety from an acceptor. Such variants will have at least 60%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% identity or greater to the naturally occurring sulfatase as measured using software programs known in the art, for example those described in Current Protocols in Molecular Biology (F. M. Ausubel et al., eds., 1987) Supplement 30, section 7.7.18. A preferred alignment program is ALIGN Plus (Scientific and Educational Software, Pennsylvania), preferably using default parameters, which are as follows: mismatch = 2; open gap = 0; extend gap = 2. [0062] The present invention also encompasses the use of fragments of mammalian sulfl and/or mammalian sulf2 that are capable of releasing a sulfate from a sulfated acceptor molecule. In some examples, a sulfatase fragment comprises an amino acid sequence from about amino acid 42 to about amino acid 389 or from about amino acid 42 to about amino acid 415 of mammalian sulfl or sulf2 disclosed in U.S. 2003/0147857. See also Morimoto-Tomita et al. 2002, J. Biol. Chem. 277:49175-85. Additional fragments of sulfatases for use in the methods of the present invention can be determined by those of skill in the art by employing routine assays that detect the release of sulfate moieties from acceptor molecules. [0063] The present invention encompasses methods for determining whether an agent modulates the activity of a sulfatase polypeptide that comprise the use of any sulfatase, or a fragment thereof that is capable of releasing a sulfate moiety from an acceptor, providing that the appropriate acceptor is selected for use with the particular sulfatase. Particular sulfatases and their in vivo and/or in vitro acceptor molecules are disclosed herein. Sulfate Acceptor and Donors Acceptor [0064] The term "acceptor" or "acceptor molecule" as used interchangeable herein, refers to a compound or molecule that is modified by either the addition of a sulfate moiety (for use in a sulfotransferase screening method) or release of a sulfate moiety (for use in a sulfatase screening method) via the catalytic activity of a sulfotransferase polypeptide or sulfatase polypeptide, respectively. Sulfotransferases and sulfatases vary in activity with respect to the donor and/or acceptor compounds with which they work. As will be understood by those of skill in the art, a variety of compounds and molecules can serve as sulfate acceptor molecules for sulfotransferases including naturally occurring biological molecules and structures, such as selectin ligands, carbohydrate structures present on selectin ligand epitopes, glycoproteins, glycolipids; synthetic molecules and structures, such as synthetic carbohydrate structures including mono-, di-, tri-, or oligomeric structure forms. A variety of compounds and molecules can serve as sulfate acceptor molecules for sulfatases including nucleophiles capable of accepting sulfate, such as phenol groups. In some examples, the acceptor comprises a detectable label, which may be directly linked or indirectly linked to the acceptor compound and which may be added to the acceptor before, after or simultaneous with the separation step. In some examples disclosed herein, an acceptor molecule is a synthetic carbohydrate GIcNAc (as shown in Figs. IA-I B) labeled with a fluorophor (and having a neutral charge) that accepts the transfer of a sulfate moiety due to the catalytic activity of GST-3. Synthetic carbohydrate acceptors for use in the methods of the present invention may be in monomeric, dimeric, trimeric or oligomeric structure form. Examples of sulfate moiety acceptors and their respective sulfotransferases are shown in Table II. It is contemplated that other complex sugars modeled after the sugar structures found in naturally occurring sulfotransferase substrates can be used in the present invention. Table II

Examples of sulfated carbohydrate epitopes, the responsible sulfotransferases, and their

biological functions.

Biological and Sulfated carbohydrate epitope Sulfotransferases (STs) pathological roles

GlcNAc-6-STs, Gal-6-ST LymPjocyte homing> inflammation

Pharmacokinetics of GalNAc-4-ST pituitary hormones

GlcUA-3-ST Neuronal development

Cell adhesion,

signaling

Inflammation, tumor Heparin/heparan sulfate STs growth and metastasis, viral infection

Chemoldne activation, development and Chondroitin sulfate STs maintenance of cartilage Cartilage maintenance, Keratan sulfate STs corneal physiology

Mycobacterial Trehalose-2-ST virulence

[0065] Additional acceptor molecules, for use with sulfotransferases and sulfatases include any uncharged oligosaccharide that can be utilized by any specific sulfotransferase or sulfatase as natural or synthetic substrates as long as the substrate recognition by the enzyme is not impaired following chemical derivatization of said oligosaccharide as its reducing end. [0066] In some examples of the present invention, the sulfotransferase is a glycosylsulfotransferase, such as for example, GST-3, or fragment thereof capable of catalyzing transfer of a sulfate moiety from a donor to an acceptor molecule, as described herein and the acceptor molecule is a monomeric form of a synthetic carbohydrate labeled with a fluorophor and capable of accepting a single sulfate moiety which facilitates ease of separation on an anion exchange column and detection. The detection of the fluorophor is by spectral methods known to one of skill in the art. The present invention is particularly advantageous as it provides a screening method that is amenable to robotics manipulation, implementation using any device capable of implementing the methods, such as (but not limited to) electronic computational devices, including computers of all types, which allows for rapid, high throughput, quantitative screening of test agents and does not rely on radioactive materials for detection. [0067] In some examples, acceptor compounds or molecules will be used within a concentration range which results in a linear increase in reaction velocity with increasing acceptor concentration. In some examples, the acceptor compound can be used at saturating levels such that the reaction is independent of acceptor concentration. In some examples, the acceptor molecule or compound is present in the assay in a concentration range of at least about 1 , at least about 5, at least about 10, at least about 20, at least about 50 and at least about 100 μM and up to about 50, up to about 75, up to about 100, up to about 250, up to about 500, up to about 750, up to about 1000 μM, up to about 2mM, up to about 3mM, up to about 4mM, or up to about 5mM and in some examples is between about 1 to about 1000 μM, between about 10 to about 500 μM or between about 50 to about 100 μM. One of skill in the art would be able to determine additional ranges and optimized ranges of an acceptor molecule to be used in the methods of the present invention based on the use of particular sulfotransferase/acceptor pairs or sulfatase/acceptor pairs. Sulfate donors [0068] The present invention encompasses the use of any donor capable of donating a sulfate moiety to an acceptor. In some examples, 3'-phosphoadenosine-5-phosphosulfate (PAPS) is the sulfate donor. [0069] In some examples, sulfate donors will be used within a concentration range which results in a linear increase in reaction velocity with increasing donor concentration. In some examples, the donor compound can be used at saturated levels such that the reaction velocity is independent of donor concentration. In some examples, the donor is present in the assay in a concentration range of at least about 0.1 μM, at least about lμM, at least about 5μM, at least about lOμM, at least about 20μM, at least about 50μM and at least about 100 μM and up to about 50μM, up to about 75μM, up to about lOOμM, up to about 250μM, up to about 500μM, up to about 750μM, and up to about ImM and in some examples is between about l μM to about ImM, between about lOμM to about 500 μM or between about 50μM to about 100 μM. One of skill in the art would be able to determine additional ranges and optimized ranges of a donor, such as PAPS, to be used in the methods of the present invention based on the use of particular sulfotransferase/acceptor pairs or sulfatase/acceptor pairs. Detectable labels [0070] In some examples of the present invention, an acceptor comprises a detectable label which facilitates detection. Detectable labels can be added to an acceptor molecule prior to separation, simultaneous with separation or after separation. Detectable labels are well known to one of skill in the art and the present invention encompasses the use of any detectable label as long as the charge of the detectable label does not interfere with the separation of the neutrally charged non-sulfated acceptor from the negatively charge sulfated acceptor. A detectable label can be directly or indirectly linked to an acceptor by methods deemed routine to the skilled artisan. The acceptor molecules can be labeled with a variety of labeling moieties including fluorescent and visible markers to name a few. In some examples, the acceptor is labeled with a fluorescent moiety. In some examples, the fluorescent moiety has a neutral charge, such as for example, coumarin or a coumarin derivative, which facilitates ease of separation of the neutrally charged non-sulfated acceptor from the negatively charged sulfated acceptor. Additional neutrally charged fluorescent moieties include dansyl, dapoxyl, BODIPY, naphthalene, quinoline, dabcyl, bimane. [0071] In illustrative examples disclosed herein in the Examples, a fluorescent derivative of GIcNAc was synthesized by linking a coumarin-based fluorophore to the sugar through a short ethanolamine linker extending from the anomeric position using standard carbohydrate and peptide coupling chemistry. In terms of spectral properties, the fluorescent GIcNAc derivative was found to have a maximal wavelength of excitation at 423 nm and a maximal wavelength of emission at 470 nm. Other neutrally charged fluorescent markers such as dansyl, dapoxyl, BODIPY, quinoline, dabcyl, bimane, phenols, naphthalene can be used in the methods of the present invention. ■ • • i • In other examples, other types of labels or markers that are detectable in visible wavelengths can be used, and include for example chromophors. [0072J It is to be understood that this invention is not limited to particular examples disclosed herein, as such may vary. It is also to be understood that the examples are not intended to be limiting since the scope of the present invention is delineated by the appended claims. EXAMPLES Example 1 : Preparation of a synthetic acceptor molecule [0073] Synthesis of a fluorescent derivative of GIcNAc, a substrate for GST-3, was achieved by tethering a coumarin-based fluorophore to the sugar through a short ethanolamine linker extending from the anomeric position using standard carbohydrate and peptide coupling chemistry. The resulting compound was evaluated as a substrate for GST-3 using a radiolabled TLC assay and was shown to be capable of accepting 35S-labled sulfate from PAPS in the presence of the enzyme. The Km of the substrate for the enzyme was also determined by the TLC assay and found to range from 32-57 μM. Elution studies of this compound after incubation with 33S-PAPS and GST-3 showed complete retention of the sulfated product on the anion exchange resin with no significant reactivity detected in the eluent. In terms of spectral properties, the fluorescent GIcNAc derivative (CmGIcNAc) was found to have a maximal wavelength of excitation at 423 nm and a maximal wavelength of emission at 470 nm. Example 2: Assay for detecting modulators of GST-2 and GST-3 (Fluorescence) Assay method [0074] Activity assays for GST-2 and GST-3 were performed in 96-well plates in a total reaction volume of 25 uL per well. All concentrations given are of the final concentration in this reaction volume. Reactions were initiated by the addition of enzyme (full length or catalytic fragment thereof) to a cocktail of HEPES (30 mM), pH 6.5; magnesium acetate (2 niM); sodium fluoride (10 uM); PAPS (1 uM) and a fluorescent derivative of the GIcNAc acceptor substrate (7-DEACmGlcNAc, 40 uM). After incubation at room temperature for two hours, the reactions were then quenched by the addition of 6 M urea (25 uL) to each well. Further dilution through the addition of 175 uL of water brought the total volume to 225 uL. A portion (200 uL) of this quenched reaction mixture was then transferred into 96-well Corning black filter plates containing 2.5 mg of hydrated QAE Sephadex A-25 per well. After the application of vacuum to remove the liquid, the resin was washed further with 3 x 200 uL of water followed by 2 x 200 uL methanol. The resin-containing filter plate was then allowed to dry before the fluorescence from the sulfated 7-DEACmGlcNAc product was recorded (λexcite = 425 nm, λemmission = 470 nm, λcutoff ~ 455 nm) on a SpectraMax Gemini XS 96-well fluorescence plate reader. Synthesis of 7-DEACmGlcNAc [0075] The synthesis of 7-DEACmGlcNAc, 33-53 (a fluorescent derivative of 2-deoxy-2- acetamido-α-D-glucose) from commercially available D-glucosamine hydrochloride is outlined in Scheme 1. After protection of the amino and hydroxyl groups of glucosamine with the Troc and acetate protecting groups respectively, the resulting sugar (40-22) was then brominated to yield the glycosyl donor 33-34. The installation of a short linker onto the sugar was then achieved via glycosylation of an N-FMOC protected ethanolamine with this glycosyl donor, yielding 33-42. After replacement of the Troc group for an acetamido group at the 2-amino position followed by the subsequent deprotection of the FMOC group on the linker, the resulting glycoside (33-47) was then ready to be coupled to the 7-diethylaminocoumarin 3-carboxylic acid fluorophore to yield 33-51. Deprotection of the acetates afforded the desired fluorescent derivative of the GIcNAc acceptor substrate (33-53) for GST-2 and GST-3. Scheme 1.

I 1 1 oc-Cl, NaHCQ V / AcOH 2 λcjO. pj πdine

40-22 33-34

AgOTf

33-42 33-46

Example 3: Validation of a fluorescent based assay [0076] As a means of validating a fluorescent based assay, the Michaelis constants for the reaction of GST-3 with both CmGIcNAc and PAPS were determined. From the plots of rate as a function of concentration for both these substrates (Figs.2A-2B), the Km values that were obtained for CmGIcNAc (25-48 μM) and PAPS (2-3 μM) proved to be highly consistent with values obtained previously wit the radioactive assay. Inhibition studies were also performed using a fluorescent-based assay. From the curves shown in Figs 4A-4B, the IC50 values for PAP, and CoA, were calculated to be 2 and 10 μM, respectively. These values are consistent with those obtained with these same compounds using the radioactive assay. Example 4 Activity assay for GST-O (Fluorescence) Assay [0077] Activity assays for GST-O were performed in 96-well plates in a total reaction volume of 25 uL per well. All concentrations given are of the final concentration in this reaction volume. Reactions were initiated by the addition of enzyme to a cocktail of HEPES (25 mM), pH 6.5; magnesium acetate (2 mM); PAPS (10 uM); protamine (200 ug/mL) and a fluorescent derivative of the lactose acceptor substrate (Lac-(9)-7DEACm, 500 uM). After incubation at room temperature for a given period of time, the reactions were then quenched by the addition of 6 M urea (25 uL) to each well. Further dilution through the addition of 175 uL of water brought the total volume to 225 uL. A portion (200 uL) of this quenched reaction mixture was then transferred into 96-well Corning black filter plates containing 2.5 mg of hydrated QAE Sephadex A-25 per well. After the application of vacuum to remove the liquid, the resin was washed further with 3 x 200 uL of water followed by 2 x 200 uL methanol. The resin-containing filter plate was then allowed to dry before the fluorescence from the sulfated Lac-(9)-7DEACm product was recorded (λexcjte = 425 nm, λemmjSSjOn = 470 nm, λcutOff = 455 nm) on a SpectraMax Gemini XS 96-well fluorescence plate reader. Synthesis of Lac-(9)-7DEACm [0078] The synthesis of Lac-(9)-7DEACm from commercially available lactose is outlined below in Scheme 2. After initial protection of the free hydroxyl groups of lactose, the installation of a short ethanolamine linker was then accomplished by conversion of the resulting peracetylated lactose into the corresponding glycosyl bromide followed by coupling to Fmoc- protected ethanolamine to yield L Following deprotection of the Fmoc group from 7, the linker was then elongated by coupling to 6-Boc-aminohexanoic acid to yield 2. The subsequent removal of the Boc group allowed the lactose moiety to be coupled to the 7- diethylaminocoumarin fluorophore. Deprotection of the acetates yielded the desired compound J for use as a substrate for GST-O. Scheme 2.

Activity for GST-I in the above fluorescent assay was not shown. This is believed by the inventors to be due to the enzyme preparation and not due to the substrate. It is believed by the inventors that the above substrate can be used for GST-I . Example 5: Catalytic fragments of GST-3 [0079] The sequence of GST-3 is disclosed in U. S. Patent No. 6,265,192 Figure 2 and below. Based on this sequence, a fragment of GST-3 from amino acid residue 30 (asparagine) to the C- terminal residue 386 (histidine) (N30-H386) is active in the assay described herein in Example 2. That is, the fragment of GST-3 from amino acid residue 30 (asparagine) to the C-terminal residue 386 (histidine) (N30-H386) is capable of transferring a sulfate moiety from a donor to an acceptor. |0080] The amino acid sequence of GST-3 is shown below in SEQ ID NO: 1. mllpkkmkll lflvsqmail alffhmysh NISSLSMKAQPERMHVLVLSSSWRSGSSFVGQLFGQHPDVFYLMEPAWHVWMMTFKQ STQA WMLHMAVRDLIRA VFLCDMSVFDDA YMEPGPRRQSSLFQWENSRALCSAPACD IIIPQDEIIPRAHCRLLCSQQPFEVVEKACRSSYSHVVLKEVRFFNLQSLYPLLKDPSLN LH IIVHLVRDPRAVFRSRERTKGDLMIDSRIVMGGQHEQKLKKEDQPYYVMQVICQSQLEI YKTIIQSLPKALQERYLLVRYEDLARAPVAQTSRMMYEFVGLEFLPHLQTVWHNITRGK GMGDHAFFHTNARDALNVSQAWRWSLPYEKVSRLQKACCGDAMNLLG YRHVRSEQE QRNLLLDLLSTWTTVPEQIH Annotations: ml = methionine 1 ; first residue in the protein. The first 29 residues of the protein are in lower case. N = asparagine 30; N linked glycosylation site required for expression; mutation to amino acid glutamine reduced expression in a Baculovirus expression system. K = lysine 37; constructs with deletions starting at K37 show reduced activity in the assay described in Example 2. A deletion starting at histidine 44 is inactive. N = asparagine 308; N linked glycosylation site required for expression; mutation to amino acid glutamine reduced expression in a Baculovirus expression system. N = asparagine 329; N linked glycosylation site not required for expression; mutation to amino acid glutamine did not affect expression in a Baculovirus expression system. H = histidine 386; last residue in the protein. Example 6: Catalytic fragment of GST-2 [0081] The sequence of GST-2 is provided at GenBank number NP 004258 and is provided below in SEQ ID NO:2. msrspqralp pgalprllqa apaaaprall pqwprrpgrr wpasplgmkv frrkalvlcagyalllvltm lnll DYKWHK EPLQQCNPDG PLGAAAGAAG GSWGRPGPPP AGPPRAHARLDLRTPYRPPA AAVGAAPAAA AGMAGVAAPP GNGTRGTGGV GDKRQLVYVF TTWRSGSSFFGELFNQNPEV FFLYEPVWHV WQKLYPGDAV SLQGAARDML SALYRCDLSV FQLYSPAGSGGRNLTTLGIF GAATNKVVCS SPLCPAYRKE VVGLVDDRVC KKCPPQRLAR FEEECRKYRT LVIKGVRVFD VAVLAPLLRD PALDLKVIHL VRDPRAVASS RIRSRHGLIR ESL QVVRSRDPRAHRMPFLEAAGHKLGAKKEGVGGPADYHALGAMEVICNSMAK TLQTALQPPDWLQGHYLVVRYEDLVG DPVKTLRRVY DFVGLLVSPE MEQFALNMTS GSGSSSKPFV VSARNATQAA NAWRTALTFQ QIKQVEEFCY QPMAVLGYER VNSPEEVKDL SKTLLRKPRL (530) [0082] Based on this sequence, an amino acid fragment of GST-2 from amino acid residue D75 (Aspartic Acid or D) to amino acid residue 530 (Leucine) had catalytic activity in the assay described in Example 2. [0083] Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity and understanding, it is readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto without departing from the spirit or scope of the appended claims.