Map 2: Biosynthetic Pathways of O-Glycans

Abstract

O-Glycosylation is a common covalent modification of Ser and Thr residues of mammalian glycoproteins. In addition to mucin-type O-glycans, there are several types of non-mucin-type O-glycans, including α-linked O-Fuc, β-linked O-Xyl, α-linked O-Man, β-linked O-GlcNAc, and so on. In this section, however, the term O-glycan refers to mucin-type O-glycans. O-Linked mucin-type oligosaccharides are not preassembled on a dolichol derivative, but every sugar is transferred individually from a specific nucleotide sugar. O-Glycosylation is initiated by the transfer of GalNAc to Thr or Ser of the polypeptide. Eight O-glycan core structures can be biosynthesized, followed by elongation and terminal glycosylation as shown in Fig. 148.1.