Serine protease of trypsin-like cleavage specificity. Synthesized in a zymogen form, proacrosin and stored in the acrosome (By similarity). Preferential cleavage: Arg-|-Xaa, Lys-|-Xaa. Inhibited by aprotinin, ovomucoid, soybean trypsin inhibitor, benzamidine, p-aminobenzamidine, and zinc ions. Activity also inhibited by a Kazal-type proteinase inhibitor. Optimum pH is 8.0-8.5. Active between 20.0-37.0 degrees Celsius. Activity increases above 25 degrees Celsius. Heavy chain (catalytic) and a light chain linked by two disulfide bonds. Glycosylated. On the 2D-gel the determined pI of this protein is: 6.4. Belongs to the peptidase S1 family.