Retinol dehydrogenase 8 is an enzyme that in humans is encoded by the ''RDH8'' gene. All-trans-retinol dehydrogenase (RDH8) is a visual cycle enzyme that reduces all-trans- retinal to all-trans-retinol in the presence of NADPH. It is a member of the short chain dehydrogenase/reductase family and is located in the outer segments of the

photoreceptor cell A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiatio ...

s; hence it is also known as photoreceptor retinol dehydrogenase. It is important in the visual cycle by beginning the rhodopsin regeneration pathway by reducing all-trans-retinal, the product of bleached and hydrolysed

rhodopsin Rhodopsin, also known as visual purple, is a protein encoded by the RHO gene and a G-protein-coupled receptor (GPCR). It is the opsin of the rod cells in the retina and a light-sensitive receptor protein that triggers visual phototransduction ...

. This is a rate-limiting step in the visual cycle. upplied by OMIMref name="entrez" />

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