Summary: In enzymology, a 12alpha-hydroxysteroid dehydrogenase (EC 1.1.1.176) is an enzyme that catalyzes the chemical reaction:3alpha,7alpha,12alpha-trihydroxy-5beta-cholanate + NADP+↔ 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholanate + NADPH + H+. Thus, the two substrates of this enzyme are 3alpha,7alpha,12alpha-trihydroxy-5beta-cholanate and NADP+, whereas its 3 products are 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholanate, NADPH, and H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. This enzyme is involved in a metabolic pathway that degrades bile acids into cholesterol.