Purification of human seminal acrosin inhibitor and its kinetics

A low molecular mass, naturally occurring acrosin inhibitor has been identified and purified (490·7-fold) from human semen, and kinetic studies have been performed on the association characteristics as well as for the determination of affinity constants (Ki values). The results show that Ki value (3·34 × 10-2) of the inhibitor towards human acrosin is almost three times lower than that of pancreatic trypsin, indicating a much higher specificity and inhibitory property for acrosin. The purified human seminal acrosin inhibitor has a molecular mass of 5·5 kDa and shows a single band using 10-20% gradient SDS PAGE. The work is of great significance for the development of more specific, nontoxic and irreversible inhibitors for human acrosin.