Properties of Testosterone 5α-Reductase of Purified Nuclear Fraction from Ventral Prostate of Rats

It was found that more than half of the activity of testosterone 5α-reduction was attached to nuclear fraction of rat ventral prostate, and some properties of this reaction were investigated using purified nuclear fraction of the gland.The optimum pH for reduction of testosterone was about 7.2 and required NADPH as a donor of reducing equivalent. Apparent km of nuclear 5α-reductase was 3.2×10-5M for testosterone and 3.0×10-4M for NADPH. Apparent Km for 19-nortestosterone was similar to that for testosterone, but the value for androst-4-ene-3, 17-dione was higher than that for testosterone.Natural and synthetic estrogenic compounds showed their inhibitory effect on the rate of testosterone 5α-reduction, but one of the gestagen and of anti-androgen did not inhibit the reaction. Estradiol-17β exhibited a most profound inhibition among the compounds examined, and the double reciprocal plots revealed that type of the inhibition is competitive.The reverse reaction of 5α-reductase using NADP or phenazine dimethyl sulfate as electron acceptor was not detected in purified nuclear fraction from rat ventral prostate.