SOME EFFECTS OF ZONA-PELLUCIDA GLYCOPROTEINS AND SULFATED POLYMERS ONTHE AUTOACTIVATION OF BOAR SPERM PROACROSIN AND ACTIVITY OF BETA-ACROSIN

The effects of zona pellucida glycoproteins, sulfated polymers and non -sulfated polymers on the activation kinetics of boar sperm proacrosin to beta-acrosin have been investigated. The aim has been to understan d more about the behaviour and function of this protein after it has b een released from the acrosome at the time of fertilization. Purified proacrosin was allowed to autoactivate at pH 8.0 in the presence of di fferent concentrations of homologous zona glycoproteins, sulfated poly mers (fucoidan, chondroitin sulfates A, B and C, dextran sulfate, poly vinylsulfate and heparin) and non-sulfated polymers (dextran, polyviny lphosphate and hyaluronic acid). Enzyme activity was measured against N-benzoyl-L-arginine p-nitroanalide substrate and changes in molecular mass of the protein monitored by SDS-PAGE. Results show that zona pel lucida glycoproteins, fucoidan, dextran sulfate and polyvinylsulfate a ll potentiate the conversion of proacrosin to beta-acrosin but subsequ ently inhibit its amidase activity. Dextran, polyvinylphosphate, chond roitin sulfates A, B and C and glucose-6-sulfate, on the other hand, e ither have no effect on autoactivation and beta-acrosin activity, or e nhance it slightly. SDS-PAGE analysis confirmed these observations and further indicated that binding of sulfated polymers to proacrosin inh ibited staining by Coomassie Blue. These results are consistent with t he hypothesis that binding of zona pellucida glycoproteins and sulfate d compounds to proacrosin/acrosin is stereospecific and that contact a ctivation onto soluble 'surfaces' causes conformational changes that a re responsible for potentiation or inhibition of activation. The impli cations of these findings for sperm binding and penetration of the zon a pellucida are discussed.