A Kunitz type of proteinase inhibitor isolated from boar seminal vesicle fluid.

Using immunoaffinity chromatography on a Sepharose 4B column with adsorbed antibodies to the basic inhibitor in bovine organs (Kunitz-type), a proteinase inhibitor was isolated from boar seminal vesicle fluid. The isolated protein inhibited acrosin, trypsin, plasmin and chymotrypsin, but not kallikrein. Its molecular weight determined by gel filtration on Sephadex G-50 was 9,500 (+/- 500) and by SDS electrophoresis in polyacrylamide gel 12,000 (+/- 500) daltons. The protein was demonstrated by immunoprecipitation only in boar seminal vesicle fluid and seminal plasma, and by indirect immunofluorescence on ejaculated spermatozoa and in the epithelium of boar seminal vesicles. This inhibitor is the first acrosin inhibitor specific for the genital organs, which evidently belongs to the group of Kunitz type inhibitors, to be described.