Our results clearly demonstrated that sperm extrac- tion without NPGB leads to proacrosin activation and the appearance of acrosins I and II which are active forms and measured using amidase assay. The presence of proteinases with a molecular weight in the range of 41 to 30 kDa in sperm extract without inhibitors was also discovered using the gelatin SDS-PAGE technique [6,18]. Richardson et al. [27] found that the extraction of turkey spermatozoa resulted in the obtaining of a large amount of acrosin in its active form, and conse- quently they concluded that acrosin is present in turkey sperm in the active form. However, these authors did not use proteinase inhibitors during extraction, so free acrosin was likely produced during the extraction pro- cedures. The results of the present study and our pre- vious one [6] strongly suggest that the proacrosin/ac- rosin system is present in turkey spermatozoa.
Kazal family inhibitors are present in turkey seminal plasma and belong to low molecular weight serine proteinase inhibitors [7]. These inhibitors form a tight, reversible complex with turkey acrosin (the equilibrium association constant value was 7.6 107 M 1), which strongly suggests that acrosin can be a target enzyme under physiological conditions [6]. In this study we demonstrated for the first time that the presence of Kazal inhibitors during extraction indeed leads to inhi- bition of proacrosin activation. This suggests that Kazal inhibitors are involved in the control of proacrosin system activation in turkey spermatozoa. We also found that during extraction active acrosin appeared despite the presence of Kazal inhibitors. This indicates that in the condition of extraction, NPGB more effi- ciently inhibits proacrosin activation than Kazal inhib- itors.
In our study we found an increase in sperm extracted amidase activity during liquid storage, what suggested the activation of the proacrosin/acrosin system. Ac