Gonadal steroid sulfates and sulfatase : V. Human testicular steroid sulfatase: Partial characterization and possible regulation by free steroids

Abstract

To elucidate the role of steroid sulfates as precursors of biologically active hormone in the human testis, cleavage of pregnenolone sulfate, dehydroepiandrosterone sulfate and androstenediol-3-sulfate by microsomal preparations was studied. The respective apparent Km values were 0.73 [mu]M, 3.85 [mu]M and 3.13 [mu]M. Evidence is presented that the three steroid sulfates are cleaved by the same enzyme.A number of free steroids were found to inhibit the steroid sulfatase activity. Among 14 C21 steroids investigated, 5-pregnen-3[beta],21-diol-20-one and 5-pregnene-3[beta]-20[alpha]-diol were the most potent inhibitors. The inhibitory effect of C21 steroids was decreased by structural alterations, e.g. a [Delta]4-3-keto for a [Delta]5-3[beta]-hydroxy configuration, 5[alpha]-reduction of the A ring, substitution of a 20[beta] for a 20[alpha]-hydroxyl group, or a 3[alpha]- for a 3[beta]-hydroxyl group. Among 9 C19 steroids investigated, 5[alpha]-androstane-3[alpha],-17[beta]-diol was the most potent inhibitor. 5[alpha] reduction of ring A of C19 steroids either increased or did not change their inhibitory effect.The kinetics of inhibition of the testicular steroid sulfatase by free steroids is consistent with partial competitive inhibition, and suggests that modulation of this sulfatase activity by free steroids may regulate release of essential free steroid precursors of testosterone.