摘要：NADPH-dependent 5α-dihydrotestosterone 3β-hydroxysteroid dehydrogenase (3β-HSD) was purified to apparent homogeneity from mature pig testicular cytosol. The purified enzyme catalyzed the conversion of 5α-dihydrotestosterone (5α-DHT) to 5α-androstane-3β, 17β-diol. The molecular weight was estimated to be 31 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 28 kDa by gel filtration chromatography, indicating that the native 3β-HSD is a monomer. The isoelectric point of the purified enzyme was 5.8 as determined by chromatofocusing. The purified enzyme reduced not only 5α-DHT but also 5β-DHT, 5α (or 5β)-androstanedione, 5α (or 5β)-dihydroprogesterone, prostaglandin E1, 13, 14-dihydro-15-keto-prostaglandin F2α, glycelaldehyde, xylose and glucuronic acid. Moreover, the enzyme reduced other carbonyl compounds including aromatic aldehydes, aromatic ketones and quinones such as 4-nitrobenzaldehyde, 4-benzoylpyridine, phenylglyoxal, cyclohexanone and 9, 10-phenanthrenequinone at high rates when compared with steroids, prostaglandins and sugars. The purified enzyme was inhibited by AgNO3, SH-reagent, disulfiram, hexesterol, stilbestrol, disulfiram and divalent cations such as Cu2+, Hg2+, Cd2+ and Co2+. Furthermore, the enzymatic properties of the purified enzyme, including catalytic activity, inhibitory effects by various agents and immunological properties, were compared with those of 3α/β-HSD enzymes from pig testicular cytosol.
