Retinol dehydrogenase with a clear preference for NADP (PubMed:12807874, PubMed:29567832). Displays high activity towards 9-cis, 11-cis and all-trans-retinol, and to a lesser extent on 13-cis-retinol (By similarity) (PubMed:12807874). Exhibits also reductive activity towards toxic lipid peroxidation products such as medium-chain aldehydes trans-2-nonenal, nonanal, and cis-6-nonenal (PubMed:12807874). Has no dehydrogenase activity towards steroid (PubMed:12807874). Seems to be required for homeostasis of retinol in liver and testis (PubMed:29567832). all-trans-retinol + NADP(+) = all-trans-retinal + H(+) + NADPH 11-cis-retinol + NADP(+) = 11-cis-retinal + H(+) + NADPH 9-cis-retinol + NADP(+) = 9-cis-retinal + H(+) + NADPH 13-cis-retinol + NADP(+) = 13-cis-retinal + H(+) + NADPH a medium-chain primary fatty alcohol + NADP(+) = a medium-chain fatty aldehyde + H(+) + NADPH (2E,6Z)-nona-2,6-dien-1-ol + NADP(+) = (2E,6Z)-nona-2,6-dienal + H(+) + NADPH (E)-oct-2-en-1-ol + NADP(+) = (2E)-octenal + H(+) + NADPH (E)-non-2-en-1-ol + NADP(+) = (E)-non-2-enal + H(+) + NADPH heptan-1-ol + NADP(+) = H(+) + heptanal + NADPH hexan-1-ol + NADP(+) = H(+) + hexanal + NADPH decan-1-ol + NADP(+) = decanal + H(+) + NADPH NADP(+) + nonan-1-ol = H(+) + NADPH + nonanal NADP(+) + octan-1-ol = H(+) + NADPH + octanal (Z)-non-6-en-1-ol + NADP(+) = (Z)-non-6-enal + H(+) + NADPH kcat is 167 min(-1) for NADPH as substrate. Optimum pH is between 6.5 and 7.5 for nonanal as substrate. Cofactor metabolism; retinol metabolism. A number of isoforms are produced. Expressed at high level in liver and testis (PubMed:12807874, PubMed:15790565, PubMed:29567832). Expressed at lower levels in smooth muscle, thymus, submaxillary gland and epididymis. In testis, expression is restricted to pachytene spermatocytes. Also expressed in four layers of the retina, including the outer segment of rods and cones (PubMed:12807874, PubMed:15790565). Down-regulated in liver by fasting and rose by refeeding. Not glycosylated. Deficient mice are fertile and developed normally but exhibit delayed dark adaptation vision (PubMed:15790565). Testis and livers of deficient mice exhibit a lower rate of all-trans-retinal conversion to all-trans-retinol (PubMed:29567832). Shows clear specificity for the pro-S hydrogen on C4 of NADPH and the pro-R hydrogen on C15 of retinols. Belongs to the short-chain dehydrogenases/reductases (SDR) family.