A new acrosin inhibitor was isolated to apparent homogeneity from the fluid of boar seminal vesicles. The inhibitor is immunologically related to the polyvalent trypsin-kallikrein inhibitor from bovine lung known as aprotinin. A crude preparation of the acrosin inhibitor was prepared by immunoaffinity chromatography on anti-aprotinin antibodies bound to Sepharose 4B column. The inhibitor was further purified by affinity chromatography on trypsin immobilized on a Sepharose 4B column, by ion-exchange chromatography on CM-Sephadex C-25, and by reversed-phase high-performance liquid chromatography on a C18 column. The relative molecular mass (Mr) of the inhibitor is about 7,000 as estimated from dodecyl sulfate-polyacrylamide gel electrophoresis. Its amino-acid composition was determined, the sequence of the first 8 amino-acid residues from the N-terminus is Thr-Arg-Asp-Phe-Pro-Pro-Asp-Gly-...

Institute of Molecular Genetics Czechoslovak Academy of Sciences Prague