PURPOSE: To obtain a large amount of purified enzyme, by using human placenta as a raw material, preparing an enzyme solution by conventional method, and purifying the solution by electrophoresis and electro-extraction.

CONSTITUTION: An enzymatic solution is prepared from human placenta by the method of Kuutti, et al, subjected to the electrophoresis on polyacrylamide gel by the method of Dauis, and the band having proline hydrase activity is separated together with the gel by the method of Hartman et al. The objective proline hydrase is extracted from the gel by the electro-extraction method of Hashigume et al. The yield is comparable to that of the method of Kuutti et al using human fetus.