The sperm hydrolytic enzyme acrosin is an acrosomal enzyme which appears to play a role in fertilization. The principal investigator's laboratory has discovered that most of the acrosin in rabbit and hamster sperm is present as its inactive zymogen precursor proacrosin. This research grant will include the use of biochemical, immunocytochemical and electron-microscopic techniques to investigate: the mechanism of proacrosin activation within hamster sperm; the intracellular sites of hamster and rabbit sperm proacrosin and acrosin; and the zymogen structure of rabbit proacrosin.