**2.3 RDHs (retinol dehydrogenases)**

RDHs are a family of dehydrogenase enzymes involved in the conversion of retinol to retinaldehyde by catalyzing the oxidation of cis-isomers of retinol, including 11-cis-, 9-cis-, and 13-cis-retinol in an NAD-dependent manner. This family of short-chain dehydrogenases/reductases functions to catalyze the final step in the biosynthesis of 11-cis retinaldehyde.
