The inhibition of acrosin by sterol sulphates

Four 3 beta-hydroxy-delta 5-steroid sulphates were found to be potent and specific inhibitors of the sperm acrosomal proteinase, acrosin. Two of these acrosin inhibitors, desmosteryl sulphate and cholesteryl sulphate, occur naturally in spermatozoa. Desmosteryl sulphate, an inhibitor of the in-vitro capacitation of hamster spermatozoa, has a Ki of 3.5 x 10(-6) M for the inhibition of acrosin. The mechanism of inhibition of sperm capacitation by sterol sulphates is probably due to their inhibition of acrosin.