Meta-Biol

• Pathways

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 (Cantagrel et al. 2010). 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 (Cantagrel et al. 2010, Kasapkara et al. 2012). 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 (Kahrizi et al. 2011). Mutations that can cause SRD5A3-CDG are Q96*, Q107*, R142*, Y163* and S10* (Al-Gazali et al. 2008, Cantagrel et al. 2010). A mutation that can cause KHRZ is F69Lfs*2 (Kahrizi et al. 2009, Kahrizi et al. 2011).