description
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

external resources
NCBI:82977
KEGG:hsa00512
PUBMED:12626393
PUBMED:11821425
PUBMED:10350056
PUBMED:10580130

genes
GALNT1 , GALNT2 , GALNT3 , GCNT1 , ST3GAL1 , ST3GAL2 , GALNT4 , GCNT3 , B4GALT5 , GALNT6 , GALNT5 , GALNT8 , C1GALT1C1 , GALNT9 , GCNT4 , GALNT7 , GALNT10 , ST6GALNAC1 , C1GALT1 , GALNT16 , GALNT11 , GALNT17 , GALNT14 , GALNT12 , GALNT13 , GALNT15 , GALNTL5 , B3GNT6 , GALNT18 , GALNTL6 , POC1B-GALNT4 ,