Dehydrodolichyl diphosphate synthaseDehydrodolichyl diphosphate synthase is an enzyme that in humans is encoded by the DHDDS gene.FunctionDehydrodolichyl diphosphate synthase catalyzes cis-prenyl chain elongation to produce the polyprenyl backbone of dolichol, a glycosyl carrier lipid required for the biosynthesis of several classes of glycoproteins.Clinical significanceIt has been suggested that missense mutations in the DHDDS gene are responsible for certain variants of retinitis pigmentosa. Since it is involved in the early steps of dolichol synthesis, vital e.g. for correct N-glycosylation, a disease caused by mutations in DHDDS should be considered a congenital disorder of glycosylation. Many CDG subtypes present with retinitis pigmentosa as a major feature.