Table 1.

Classification of the major glycan–protein linkages

Glycan type	Linkage	Typical proteins	Cell type
N-linked	GlcNAc-β-Asn	Cell surface receptors and secreted proteins	All cell types
O-linked	GalNAc-α-Ser/Thr	Secreted and cell surface mucins	Cell surface, gastrointestinal and reproductive tracts
O-linked	Man-α-Ser/Thr	α-Dystroglycan	Muscle tissue, nerve cells
O-linked	Xyl-β-Ser	Chondroitin/dermatan sulfate & heparan sulfate/heparin	Extracellular matrix, cartilage