Glycoconjugates: Structure and Biosynthesis

Abstract

Carbohydrates are frequently found attached to lipids (e.g., glycoglycerolipids and glycosphingolipids), proteins (glycoproteins and proteoglycans), or in some cases, both (glycosylphosphatidylinositol-anchored proteins). Three main types of protein modification are found in vertebrates: N-linked glycosylation, O-linked glycosylation, and the attachment of glycosylphosphatidylinositol anchors; also, a fourth rarer type, C-mannosylation, is found. In the main types, the biosynthesis of glycoconjugates occurs in two specialized, membranous biosynthetic compartments within the cell: the endoplasmic reticulum and the Golgi apparatus. Degradation of glycoconjugates occurs in another specialized m..