Multiple Forms of Human Acrosin: Isolation and Properties

Abstract

Human acrosin [EC 3.4.21.10] was purified to electrophoretically homogeneous forms by acidic extraction of washed ejaculated spermatozoa and gel filtration of the acidic extracts on Sephadex G-75, followed by affinity chromatography on p-aminobenzamidine Sepharose. Human acrosin exists in at least 4 molecular forms. The apparent MW of 3 forms were 64,000, 38,000 and 25,000, respectively. The high molecular weight forms by incubation of the acrosin preparation obtained from freshly ejaculated spermatozoa in solutions of pH near 7. Like boar acrosin, human acrosin is also a glycoprotein and reversibly bound to Concanavalin A-Sepharose. The amino acid composition of the 25,000 MW form is similar to that of human trypsin. Rabbit anti-boar-acrosin .gamma.-globulins form a precipitate with human acrosin, but not with porcine trypsin or human plasmin. The relationship between the occurrence of multiple acrosin forms and proenzyme activation by limited proteolysis is discussed.