Retinol dehydrogenase

The enzyme is mainly expressed in the retinal pigment epithelium (RPE) and is part of short-chain dehydrogenase (SDR) / reductase superfamily.

[10] In Bovine, retinol dehydrogenase is found as a part of retinal rod outer segments and shows difficulty when separating from membrane.

[11] Retinoid dehydrogenases/reductases (oxidoreductases), including retinol dehydrogenase, catalyze the key oxidation-reduction reactions in the visual cycle, converting vitamin A to 11-cis retinal, which is the chromophore of the rod and cone photoreceptors.

RDH12 is the primary enzyme that reduces all-trans retinal released from bleached photopigments during recovery phase in the visual cycle.

In vertebrates, the retinoic acid is the ligand that controls nuclear receptor signaling pathway, which is responsible for growth and development as well as epithelial maintenance, therefore can be used for cancer and acne treatment.

This can potentially explain how isotretinoin, the active ingredient is Roaccutane (Accutane), can suppress sebaceous glands and be used for severe acne treatment.

[1][16] At least 20 mutations in rdh12 gene, which encodes retinol dehydrogenase, can be associated to diseases, including severe and early-onset autosomal recessive retinal dystrophy (arRD), or Leber congenital amaurosis.

Image 1: Wild-type human sigma (class IV) alcohol dehydrogenase (1D1S) has retinol dehydrogenase activity. Zinc molecules are depicted as red balls, while NAD molecules are purple. Note that the enzyme exists as two protein units in this figure. (PDB file from RCSB ) [ 5 ]
Image 2: Wild-type human sigma (class IV) alcohol dehydrogenase (1D1S). Retinols will bind between the catalytic zinc molecules (red balls) and the NAD molecule (purple). [ 6 ] (PDB file from RCSB ) [ 5 ]
Image 3: The visual phototransduction cycle yields 11- cis -retinal from 11- cis -retinol using 11- cis -retinol dehydrogenase. [ 10 ] [ 12 ] [ 14 ]