Retinol dehydrogenase 8 is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that in humans is encoded by the ''RDH8''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. All-trans-retinol dehydrogenase (RDH8) is a

visual cycle The visual cycle is a process in the retina that replenishes the molecule retinal for its use in Visual perception, vision. Retinal is the chromophore of most visual opsins, meaning it captures the photons to begin the phototransduction cascade. W ...

enzyme that reduces all-trans-

retinal Retinal (also known as retinaldehyde) is a polyene chromophore. Retinal, bound to proteins called opsins, is the chemical basis of visual phototransduction, the light-detection stage of visual perception (vision). Some microorganisms use ret ...

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 radiation ...

s; hence it is also known as photoreceptor retinol

dehydrogenase A dehydrogenase is an enzyme belonging to the group of oxidoreductases that oxidizes a substrate by reducing an electron acceptor, usually NAD+/NADP+ or a flavin coenzyme such as FAD or FMN. Like all catalysts, they catalyze reverse as well as ...

. 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 a light-sensitive receptor protein that triggers visual phototransduction in rod cells. Rhodopsin mediates dim ...

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

References

Further reading