Acrosin is a serine protease located within mammalian
acrosome as inactive proacrosin. Sulphated polymers bind to proacrosin and acrosin, to a domain
different from the active site. Upon binding, these polymers induce proacrosin activation and some of
them, such as fucoidan, inhibit sperm binding to the zona pellucida. In this work we have studied the
interaction of solubilised zona pellucida glycoproteins (ZPGs), heparin and ARIS (Acrosome Reaction
Inducing Substance of Starfish) with boar and human acrosin. We have found that ARIS, solubilised ZPGs
and fucoidan, but not heparin, inhibit the binding of the monoclonal antibody against human acrosin
C5F10 to boar or human proacrosin. These results suggest that fucoidan, solubilised ZPGs and ARIS bind
to a related domain on the proacrosin surface. Moreover, ARIS was able to induce human proacrosin
activation. On the other hand, neither ARIS nor heparin from porcine intestinal mucosa or bovine lung
induced hamster sperm acrosome reaction or sperm motility. Recent data showed that acrosin is involved
in dispersal of the acrosomal matrix after acrosome reaction. Thus, the control of the ZPG glycan
chains over proacrosin activation may regulate both sperm penetration rate and limited proteolysis of
zona pellucida proteins.