MULTIPLE FORMS OF BOAR ACROSIN AND THEIR RELATIONSHIP TO PROENZYME ACTIVATION

Further evidence is presented that the acrosomal proteinase acrosin [EC 3.4.21.10] exists as a zymogen precursor in freshly ejaculated boar spermatozoa. Autoactivation of proacrosin to acrosin takes place optimally at slightly alkaline pH and in the presence of Ca2+. Activation is considerably accelerated by catalytic amounts of trypsin [EC 3.4.21.4] or highly purified acrosin. A significant acceleration of the activation is also achieved by porcine pancreatic and urinary kallikrein [EC 3.4.21.8]; chymotrypsin, [EC 3.4.21.1] plasmin [EC 3.4.21.7], thrombin [EC 3.4.21.5], or urokinase [EC 3.4.99.26] showed no effect. Activation can be inhibited by p-amino-benzamidine and p-nitrophenyl p-guanidinobenzoate. Electrophoretic analysis at different stages of activation revealed that during this process various molecular forms of acrosin are produced, apparently by limited proteolysis.