Cytochrome P450 26A1; A cytochrome P450 monooxygenase involved in the metabolism of all-trans retinoic acid (atRA), a signaling molecule that binds to retinoic acid receptors and regulates gene transcription. Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (CPR; NADPH- ferrihemoprotein reductase). Catalyzes the hydroxylation of carbon hydrogen bonds of atRA primarily at C-4 and C-18. Has no activity toward 9-cis and 13-cis retinoic acid st [...]

All-trans-retinol 13,14-reductase; Catalyzes the saturation of all-trans-retinol to all-trans- 13,14-dihydroretinol. Does not exhibit any activity toward all-trans- retinoic acid, nor 9-cis, 11-cis or 13-cis-retinol isomers. May play a role in the metabolism of vitamin A. Independently of retinol conversion, may regulate liver metabolism upstream of MLXIPL/ChREBP. May play a role in adipocyte differentiation. Belongs to the carotenoid/retinoid oxidoreductase family. CrtISO subfamily.

Retinol dehydrogenase 12; Retinoids dehydrogenase/reductase with a clear preference for NADP. Displays high activity towards 9-cis, 11-cis and all-trans- retinal. Shows very weak activity towards 13-cis-retinol. Also exhibits activity, albeit with lower affinity than for retinaldehydes, towards lipid peroxidation products (C9 aldehydes) such as 4-hydroxynonenal and trans-2-nonenal. May play an important function in photoreceptor cells to detoxify 4-hydroxynonenal and potentially other toxic aldehyde products resulting from lipid peroxidation. Has no dehydrogenase activity towards stero [...]

Short-chain dehydrogenase/reductase 3; Catalyzes the reduction of all-trans-retinal to all-trans- retinol in the presence of NADPH.

Retinol dehydrogenase 8; Retinol dehydrogenase with a clear preference for NADP. Converts all-trans-retinal to all-trans-retinol. May play a role in the regeneration of visual pigment at high light intensity (By similarity). Belongs to the short-chain dehydrogenases/reductases (SDR) family.

Retinol dehydrogenase 11; Retinol dehydrogenase with a clear preference for NADP. Displays high activity towards 9-cis, 11-cis and all-trans-retinol, and to a lesser extent on 13-cis-retinol. Exhibits a low reductive activity towards unsaturated medium-chain aldehydes such as cis -6-nonenal and no activity toward nonanal or 4-hydroxy-nonenal. Has no dehydrogenase activity towards steroid.

Dehydrogenase/reductase SDR family member 9; 3-alpha-hydroxysteroid dehydrogenase that converts 3-alpha- tetrahydroprogesterone (allopregnanolone) to dihydroxyprogesterone and 3-alpha-androstanediol to dihydroxyprogesterone. Plays also a role in the biosynthesis of retinoic acid from retinaldehyde. Can utilize both NADH and NADPH. Belongs to the short-chain dehydrogenases/reductases (SDR) family.

Lecithin retinol acyltransferase; Transfers the acyl group from the sn-1 position of phosphatidylcholine to all-trans retinol, producing all-trans retinyl esters. Retinyl esters are storage forms of vitamin A (Probable). LRAT plays a critical role in vision (Probable). It provides the all-trans retinyl ester substrates for the isomerohydrolase which processes the esters into 11-cis-retinol in the retinal pigment epithelium; due to a membrane-associated alcohol dehydrogenase, 11 cis-retinol is oxidized and converted into 11-cis- retinaldehyde which is the chromophore for rhodopsin and t [...]

Dehydrogenase/reductase SDR family member 4; Reduces all-trans-retinal and 9-cis retinal. Can also catalyze the oxidation of all-trans-retinol with NADP as co-factor, but with much lower efficiency. Reduces alkyl phenyl ketones and alpha- dicarbonyl compounds with aromatic rings, such as pyrimidine-4- aldehyde, 3-benzoylpyridine, 4-benzoylpyridine, menadione and 4- hexanoylpyridine. Has no activity towards aliphatic aldehydes and ketones (By similarity); Belongs to the short-chain dehydrogenases/reductases (SDR) family.