Prostate 3α-hydroxysteroid dehydrogenase: Its partial purification and properties

Abstract

3α-Hydroxysteroid dehydrogenase (E.C. 1.1.1.50) has been purified from the cytosol fraction (superna-tant fluid at 105,000 g) of rat prostate by precipitation with ammonium sulphate (40–100% saturation), followed by chromatography on DEAE-cellulose and Sephadex G-100. Electrophoretic analysis of the enzyme preparation at the final stage revealed two major protein bands which were closely located on the gel, and a few minor bands. The enzyme activity was exclusively localized in the major bands. The final preparation was purified about 190 fold in S.A., compared with the cytosol fraction precipi-tated at 40–100% of ammonium sulphate saturation. Molecular weight of the 3α-hydroxysteroid de-hydrogenase was estimated as 34,000 daltons from the elution pattern of the activity through the Sephadex G-100 gel filtration. The final enzyme preparation was devoid of receptor component with high affinity for 5α-dihydrotestosterone. Optimal temperature of the final 3α-hydroxysteroid dehydro-genase preparation at pH 7.4 was about 45–47.5°C. The enzyme preferred NADP(H) to NAD(H), and reduction of 5α-dihydrotestosterone was more efficiently catalyzed by the enzyme than oxidation of 5α-androstane-3α,17β-diol.