[Isolation and characterization of dipeptidylpeptidase IV from human seminal plasma]

Two forms of dipeptidylpeptidase IV with molecular weights (gel distribution chromatography) of 270 kD and about 1450 kD were isolated from human seminal plasma. The enzymes migrating differently in electrophoresis possess identical catalytic properties in regard to pH optimum, kinetic constants and the influence of effectors. The high-molecular form loses at 65 degrees C its enzymatic activity significantly more slowly. After 60 min of incubation at 68 degrees C, human seminal plasma has still about 12-32% (N = 50) dipeptidylpeptidase activity. Through the action of Triton X-100 or chymotrypsin the high-molecular form can be transferred into the low-molecular one without loss of activity. In 80 healthy human sperm donors the average proportion of the low-molecular form of peptidase was determined to be 9-22%.