3-alpha-hydroxysteroid dehydrogenase that converts 3-alpha-tetrahydroprogesterone (allopregnanolone) to dihydroxyprogesterone and 3-alpha-androstanediol to dihydroxyprogesterone. May play a role in the biosynthesis of retinoic acid from retinaldehyde, but seems to have low activity with retinoids. Can utilize both NADH and NADPH.
Highly expressed in trachea and epidermis. Detected at lower levels in spinal cord, bone marrow, brain, tongue, esophagus, heart, colon, testis, placenta, lung, skeletal muscle and lymph node.
Belongs to the short-chain dehydrogenases/reductases (SDR) family.
Microsome membrane. Endoplasmic reticulum membrane. Associated with microsomal membranes.