A 3-hydroxysteroid dehydrogenase which catalyzes the reversible reduction of the active androgen, DIHYDROTESTOSTERONE to 5 ALPHA-ANDROSTANE-3 ALPHA,17 BETA-DIOL. It also has activity towards other 3-alpha-hydroxysteroids and on 9-, 11- and 15- hydroxyprostaglandins. The enzyme is B-specific in reference to the orientation of reduced NAD or NADPH.

Synonyms: 5 alpha-Dihydroprogesterone 3 alpha-Hydroxysteroid Oxidoreductase, 3 alpha-Hydroxysteroid Dehydrogenase (B-Specific), NADPH 5 alpha Dihydroprogesterone 3 alpha Hydroxysteroid Oxidoreductase, 3 alpha Hydroxysteroid Oxidoreductase, NADPH-5 alpha-Dihydroprogesterone 3 alpha-Hydroxysteroid Oxidoreductase, 3-alpha-Hydroxysteroid Dehydrogenase (B-Specific), EC 1.1.1.50, 5 alpha-3 alpha-Hydroxysteroid Dehydrogenase, 3 alpha-Hydroxysteroid Oxidoreductase, Oxidoreductase, 3 alpha-Hydroxysteroid, 3 alpha-Hydroxysteroid Dehydrogenase, Dehydrogenase, 3 alpha-Hydroxysteroid, 3 alpha Hydroxysteroid Dehydrogenase, 5-DP-3 alpha-HSO, 3alpha-Hydroxysteroid Dehydrogenase (B-specific), 5 alpha Dihydroprogesterone 3 alpha Hydroxysteroid Oxidoreductase