ARTICLES

Acrosin of mouse spermatozoa

Mouse spermatozoa possess a neutral proteinase, acrosin, that is to a large extent (70-80%) present in the zymogen (proacrosin) form. Acid extraction yields higher amounts of acrosin than detergent extraction. Synthetic inhibitor studies indicate that mouse acrosin has a serine and histidine at its active site and hydrolyzes the peptide bonds of lysine and arginine but of not phenylalanine. An inhibitor of acrosin is associated with mouse spermatozoa, capable of preventing the activity of at least 60% of all available acrosin. Acrosin activity is essential for fertilization because natural and synthetic inhibitors of mouse acrosin prevent the union of the gametes. Also, the relative inhibitory activity of synthetic agents toward acrosin runs approximately parallel to their antifertility activity. The percent of acrosin in the proacrosin form does not change after capacitating mouse spermatozoa in vitro.