PURPOSE: To measure a target measurement substance in high sensitivity by an enzyme cycling by reacting a liposome having immobilized an antigen against an antibody of a target to be measured to a membrane and containing an enzyme with a complement, a coenzyme such as a thio NAD, an NAD, etc., a dehydrogenase and a specimen.

CONSTITUTION: A liposome which has immobilized an antigen against an antibody of a target measurement substance to the surface of a membrane, contains a detectable enzyme in the interior and is subjected to a membrane dissolving action with a complement is reacted with the complement, at least one of a thio NADP a thio NAD, a NADP, a NAD, etc., as a coenzyme, a dehydrogenase and a target measurement substance-containing specimen to be tested. Activity of the enzyme in the liposome made measurable by the dissolution reaction of the liposome following the activation of the complement is measured by supplying a substance formed by action of the enzyme to an enzyme cycling system of the formula (A1 is thio NANDP, thio NAD, NADP or NAD; A2 is a reduction type product of A1; B1 is a reduction type coenzyme different from A1; B2 is oxidation type product of B1 to measure the target measurement substance in the specimen to be tested in high sensitivity.