Fig. 1

De novo dolichol biosynthesis and the dolichol cycle. a Dolichol-phosphate (DolP) is synthesized from farnesyl diphosphate and isopentenyl diphosphate by enzymes encoded by genes indicated in bold capital letters. Enzymes responsible for the dephosphorlylation of dehydrodolichol diphosphate have not been characterised. During the dolichol cycle an oligosaccharide is constructed on DolP by the sequential transfer of sugars (N-acetylglucosamine; blue squares, mannose; green circles, glucose; blue circles) by glycosyltransferases and accessory proteins encoded by genes indicated on the left of the cycle in bold capital letters. The oligosaccharide Glc₃Man₉GlcNAc₂ is transferred onto protein (−N-X-S/T-) by oligosaccharyltranferase (OST) and dolichol-diphosphate (DolPP) is recycled by dolichol diphosphate phosphatase encoded by DOLPP1. b The ALG6 gene encodes Dol-P-Glc: Man₉GlcNAc₂-PP-dolichol α-1,3 glucosyltransferase