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 [...]

Retinal dehydrogenase 1; Can convert/oxidize retinaldehyde to retinoic acid. Binds free retinal and cellular retinol-binding protein-bound retinal (By similarity). May have a broader specificity and oxidize other aldehydes in vivo.

Retinal dehydrogenase 2; Converts retinaldehyde to retinoic acid. Recognizes as substrates free retinal and cellular retinol-binding protein-bound retinal. Can metabolize octanal and decanal, but has only very low activity with benzaldehyde, acetaldehyde and propanal. Displays complete lack of activity with citral (By similarity). Belongs to the aldehyde dehydrogenase family.

Beta,beta-carotene 15,15'-dioxygenase; Symmetrically cleaves beta-carotene into two molecules of retinal using a dioxygenase mechanism; Belongs to the carotenoid oxygenase family.

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 [...]

Retinol dehydrogenase 5; Catalyzes the oxidation of cis-isomers of retinol, including 11-cis-, 9-cis-, and 13-cis-retinol in an NAD-dependent manner. Has no activity towards all-trans retinal (By similarity). Plays a significant role in 11-cis retinol oxidation in the retinal pigment epithelium cells (RPE). Also recognizes steroids (androsterone, androstanediol) as its substrates. Belongs to the short-chain dehydrogenases/reductases (SDR) family.

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.

Retinoid isomerohydrolase; Critical isomerohydrolase in the retinoid cycle involved in regeneration of 11-cis-retinal, the chromophore of rod and cone opsins. Catalyzes the cleavage and isomerization of all-trans-retinyl fatty acid esters to 11-cis-retinol which is further oxidized by 11-cis retinol dehydrogenase to 11-cis-retinal for use as visual chromophore. Essential for the production of 11-cis retinal for both rod and cone photoreceptors. Also capable of catalyzing the isomerization of lutein to meso-zeaxanthin an eye- specific carotenoid. The soluble form binds vitamin A (all-tr [...]

Cytochrome P450 27C1; Catalyzes the conversion of all-trans retinol (also called vitamin A1, the precursor of 11-cis retinal) to 3,4-didehydroretinol (also called vitamin A2, the precursor of 11-cis 3,4-didehydroretinal). Also acts on all-trans retinal and all-trans retinoic acid. Belongs to the cytochrome P450 family.