Defective SRD5A3 causes SRD5A3-CDG, KHRZ

Polyprenol reductase (SRD5A3), resident on the endoplasmic reticulum membrane, normally mediates the reduction of the alpha-isoprene unit of polyprenol (pPNOL) to form dolichol (DCHOL) in a NADPH-dependent manner. DCHOLs are substrates required for the synthesis of the lipid-linked oligosaccharide (LLO) precursor used for N-glycosylation. Defects in SRD5A3 cause congenital disorder of glycosylation 1q (SRD5A3-CDG, CDG1q; MIM:612379), a neurodevelopmental disorder characterised by under-glycosylated serum glycoproteins resulting in nervous system development, psychomotor retardation, hypotonia, coagulation disorders and immunodeficiency. Defects in SRD5A3 can also cause Kahrizi syndrome (KHRZ; MIM:612713), a neurodevelopmental disorder characterised by mental retardation, cataracts, holes in eye structures, pathological curvature of the spine, and coarse facial features.

Summary from Reactome (R-HSA-4755579), read 2026-09-23.