Inhibition of Human Acrosin by Fructose and Other Monosaccharides

Acrosin (EC 3.4.21.10), isolated and purified from human spermatozoa, was inhibited by a variety of monosaccharides. Fructose was the most effective ketose inhibitor and decreased acrosin activity at concentrations as low as those which are found in semen. The most effective aldohexose tested was α-methyl mannoside and the most effective aldopentose was ribose. D-hexoses were more effective inhibitors than their L-derivatives. In contrast, D- and L-aldopentoses were approximately equal in inhibitory potency. Inhibition of acrosin by monosaccharides may explain, at least in part, the reported inhibitory effects of certain sugars on the acrosome reaction and fertilization. To date, acrosin is the only proteinase shown to be inhibited by sugars.