Aldo-keto reductase family 1 member C21 (Akr1c21)

NADP-dependent 17-alpha-hydroxysteroid dehydrogenase that converts 5-alpha-androstane-3,17-dione to androsterone. Has lower 3-alpha-hydroxysteroid dehydrogenase activity.

Has broad substrate specificity and acts on different 17-alpha- hydroxysteroids, 17-ketosteroids, 3-alpha hydroxysteroids and 3- ketosteroids. Reduction of keto groups is strictly stereoselective.