3-beta-HSD is a bifunctional enzyme, that catalyzes the oxidative conversion of Delta(5)-ene-3-beta-hydroxy steroid, and the oxidative conversion of ketosteroids. The 3-beta-HSD enzymatic system plays a crucial role in the biosynthesis of all classes of hormonal steroids. a 3beta-hydroxy-Delta(5)-steroid + NAD(+) = a 3-oxo-Delta(5)-steroid + H(+) + NADH a 3-oxo-Delta(5)-steroid = a 3-oxo-Delta(4)-steroid NAD(+) + pregnenolone = H(+) + NADH + pregn-5-ene-3,20-dione pregn-5-ene-3,20-dione = progesterone 3beta-hydroxyandrost-5-en-17-one + NAD(+) = androst-5-ene-3,17-dione + H(+) + NADH androst-5-ene-3,17-dione = androst-4-ene-3,17-dione Lipid metabolism; steroid biosynthesis. Liver and kidney. Belongs to the 3-beta-HSD family.