PARTICIPATION OF GLYCOSYLATED RESIDUES IN THE HUMAN SPERM ACROSOME REACTION - POSSIBLE ROLE OF N-ACETYLGLUCOSAMINIDASE

Sperm binding to the egg zona pellucida is mediated by complementary p rotein-carbohydrate interaction. This binding results in the exocytosi s of the sperm acrosome, or acrosome reaction (AR). We report the effe ct of different neoglycoproteins (sugar residues covalently bound to b ovine serum albumin) on the human sperm AR. p-Aminophenyl-N-acetyl-bet a-D-glucosaminide-BSA (BSA-GlcNAc) and p-aminophenyl-alpha-D-mannopyra noside-BSA (BSA-Man) at 1 mu g/ml were capable of inducing the greates t percentages of AR (3-fold stimulation with respect to controls), whi le other NeoGPs had only a weak effect on this process. The BSA-GlcNAc -induced acrosome reaction was inhibited by N-acetylglucosamine (GlcNA c), p-nitrophenyl-GlcNAc, and purified soluble beta-N-acetylglucosamin idase (beta NAG). The induction of the AR with BSA-Man could be inhibi ted by mannose, while soluble alpha-mannosidase was only partially eff ective. These data suggest that binding sites for GlcNAc and mannose m ay be involved in the induction of the AR in human sperm. The characte ristics of the BSA-GlcNAc induction suggest that the beta NAG molecule may be the mediator of this effect.