NADPH-dependent oxidoreductase which catalyzes the reduction of a variety of compounds bearing carbonyl groups including steroids, retinoids and xenobiotics ( , ). Catalyzes the reduction/inactivation of 5alpha-dihydrotestosterone to 3alpha-androstanediol, with a possible role in the modulation of androgen receptor function (, ). Involved in the reduction of all-trans-retinal to all-trans-retinol . Converts cortisone to 20beta-dihydrocortisone in vitro, although the physiological relevance of this activity is questionable . Reduces exogenous compounds such as quinones (1,2-naphtoquinone, 9,10-phenantrenequinone and benzoquinone) and other xenobiotics (alpha-diketones) in vitro, suggesting a role in the biotransformation of xenobiotics with carbonyl group (, ). A dehydrogenase activity has not been detected so far . May play a role as tumor suppressor .
Subcellular locations: Endoplasmic reticulum membrane
Bound to the endoplasmic reticulum membrane, possibly through a N-terminus anchor. The main bulk of the polypeptide chain was first reported to be facing toward the lumen of the endoplasmic reticulum . However, it was later shown to be facing the cytosol .
Found predominantly in the adrenal glands, liver, thyroid, prostate, small intestine, colon, stomach, kidney and brain . Lower levels observed in skeletal muscle, the lung and the spleen .