AFFINITY SITES FOR BETA-GLUCURONIDASE ON THE SURFACE OF HUMAN SPERMATOZOA

Glycosidases secreted by the epididymis become bound to the surface of spermatozoa during their transit through the epididymal duct. They ar e believed to play a role in mammalian fertilization. In the present r eport, we demonstrate that beta-glucuronidase binds to the surface of ejaculated human spermatozoa with high affinity and in a saturable man ner. The binding is Ca2+- independent, inhibited by either mannose-6-p hosphate, phosphomannan fragments from the yeast Hansenula holstii and alpha-mannosidase from the Dictyostelium discoideum, suggesting that phosphomannosyl receptors are involved in the recognition of the enzym e. The catalytic site of the enzyme is not involved in the binding. Th e localization of the beta-glucuronidase binding-sites is restricted t o the surface of the sperm head. These results suggest that the sperma tozoa could be the target for glycosidases present in the seminal plas ma.