Catalyzes the reversible interconversion of hydroxy and oxo groups at position 3 of the steroid nucleus. Along with the 3 alpha-hydroxysteroid dehydrogenase and 3-oxo-reductase activities towards a variety of cis or trans fused A/B ring steroids, it also reduces several xenobiotic carbonyl compounds, including a metyrapone-based class of insecticides, to the respective alcohol metabolites. No detectable activity on testosterone, progesterone or 3-oxo-desogestrel. a 3alpha-hydroxysteroid + NADP(+) = a 3-oxosteroid + H(+) + NADPH a 3alpha-hydroxysteroid + NAD(+) = a 3-oxosteroid + H(+) + NADH Homodimer. By steroids. Derepression of gene transcription occurs by binding of the steroid inducer molecule to a repressor protein. This protein is thought to initiate prokaryotic steroid catabolism. Belongs to the short-chain dehydrogenases/reductases (SDR) family.