Dolichol Phosphate

Dolichol phosphate is an isoprenoid compound (90-100 carbons total) made from dolichol (see here for synthesis of dolichol via the cholesterol biosynthetic route) by phosphorylation catalyzed by a kinase that uses CTP as the energy and phosphate source. Dolichol phosphate performs two important functions in synthesis of N-linked glycoproteins.

1. Dolichol phosphate is the structure upon which the complex oligosaccharide is made before transfer to the target protein. (The addition of the first moiety, N-acetylglucosamine from UDP-N-acetylglucosamine, can be blocked by the antibiotic, tunicamycin.) After assembly of the oligosaccharide is complete, the carbohydrate structure is transferred from dolichol phosphate to an asparagine residue of a target protein having the sequence Asn-x-Ser/Thr, where X is any amino acid.

2. Dolichol phosphate is a carrier of sugars to oligosaccharide chain synthesis assembly. Such activated sugars include dolichol-P-mannose and dolichol-P-glucose.

See also: Biosynthesis of Glycoconjugates, Figure 16.16, Figure 16.17