O-glycans are a class of glycans that modify serine or threonine residues of proteins. Biosynthesis of O-glycans starts from the transfer of N-acetylgalactosamine (GalNAc) to serine or threonine. The first GalNAc may be extended with sugars including galactose, N-acetylglucosamine, fucose, or sialic acid, but not mannose, glucose, or xylose. Depending on the sugars added, there are four common O-glycan core structures, cores 1 through 4, and an additional four, cores 5 though 8. Mucins are highly O-glycosylated glycoproteins ubiquitous in mucous secretions on cell surfaces and in body fluids. Mucin O-glycans can be branched, and many sugars or groups of sugars are antigenic. Important modifications of mucin O-glycans include O-acetylation of sialic acid and O-sulfation of galactose and N-acetylglucosamine.

Metabolism; Glycan biosynthesis and metabolism

PMID:10580130

Brockhausen I.

Pathways of O-glycan biosynthesis in cancer cells.

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Molecular cloning and characterization of a novel UDP-GlcNAc:GalNAc-peptide beta1,3-N-acetylglucosaminyltransferase (beta 3Gn-T6), an enzyme synthesizing the core 3 structure of O-glycans.

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Purification and cDNA cloning of UDP-GlcNAc:GlcNAcbeta1-3Galbeta1-4Glc(NAc)-R [GlcNAc to Gal]beta1,6N-acetylglucosaminyltransferase from rat small intestine: a major carrier of dIGnT activity in rat small intestine.

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The acceptor substrate specificity of human beta4-galactosyltransferase V indicates its potential function in O-glycosylation.

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