A bifunctional enzyme responsible for the oxidation and isomerization of 3beta-hydroxy-Delta(5)-steroid precursors to 3-oxo-Delta(4)-steroids, an essential step in steroid hormone biosynthesis. Specifically catalyzes the conversion of pregnenolone to progesterone, dehydroepiandrosterone (DHEA) to 4-androstenedione, and androstenediol to testosterone (PubMed:1537836, PubMed:1985917). Additionally, catalyzes the interconversion between 3beta-hydroxy and 3-oxo-5alpha-androstane steroids controlling the bioavalability of the active forms. Specifically converts dihydrotestosterone to its inactive form 5alpha-androstanediol, that does not bind androgen receptor/AR. Also converts androstanedione, a precursor of testosterone and estrone, to epiandrosterone (PubMed:1537836). Expected to use NAD(+) as preferred electron donor for the 3beta-hydroxy-steroid dehydrogenase activity and NADPH for the 3-ketosteroid reductase activity (Probable). a 3beta-hydroxy-Delta(5)-steroid + NAD(+) = a 3-oxo-Delta(5)-steroid + H(+) + NADH NAD(+) + pregnenolone = H(+) + NADH + pregn-5-ene-3,20-dione 3beta-hydroxyandrost-5-en-17-one + NAD(+) = androst-5-ene-3,17-dione + H(+) + NADH androst-5-en-3beta,17beta-diol + NAD(+) = 17beta-hydroxy-androst-5-en-3-one + H(+) + NADH a 3beta-hydroxysteroid + NADP(+) = a 3-oxosteroid + H(+) + NADPH 5alpha-androstane-3beta,17beta-diol + NADP(+) = 17beta-hydroxy-5alpha-androstan-3-one + H(+) + NADPH 3beta-hydroxy-5alpha-androstan-17-one + NADP(+) = 5alpha-androstan-3,17-dione + H(+) + NADPH a 3-oxo-Delta(5)-steroid = a 3-oxo-Delta(4)-steroid pregn-5-ene-3,20-dione = progesterone androst-5-ene-3,17-dione = androst-4-ene-3,17-dione 17beta-hydroxy-androst-5-en-3-one = testosterone 5alpha-androstane-3beta,17beta-diol + NAD(+) = 17beta-hydroxy-5alpha-androstan-3-one + H(+) + NADH Vmax for dihydrotestosterone reduction is 15-fold higher in the presence of NADH than in the presence of NADPH. Steroid hormone biosynthesis. Steroid metabolism. Adrenal glands, kidney, testes and ovaries. Belongs to the 3-beta-HSD family.