Zona pellucida induces conversion of proacrosin to acrosin

The effect of heat-solubilized zonae pellucidae (ZP) isolated from mature pig ovaries on the conversion of pig proacrosin to acrosin was examined and compared with the effects of different sulphated polysaccharides. At low concentrations, zona glycoproteins potently stimulated acrosin auto-activation. Up to 2.5 micrograms ml-1 ZP, the acceleration of acrosin activation was shown to be dependent on the ZP concentration. At higher concentrations zona glycoproteins exerted an inhibitory effect on acrosin amidase activity. A similar effect was demonstrated for fucoidan, heparin, and chondroitin sulphate. The results intimate that in vivo, the conversion of proacrosin to acrosin is regulated at the sperm-zona interface.