Glycoconjugate

A glycoconjugate is a biomolecule in which a carbohydrate moiety is covalently attached to another biomolecule or lipid. This structural class includes glycoproteins, proteoglycans, and glycolipids, as well as smaller entities such as glycopeptides. The carbohydrate portion can modulate folding, stability, and interactions with other molecules, influencing cell recognition and signaling.

Most glycoconjugates derive from N- or O-glycosylation. N-glycans are typically attached to asparagine in the consensus sequon; O-glycans attach to serine or threonine residues. Glycolipids contain glycans linked to lipids, forming surface components in membranes. Proteoglycans consist of a core protein covalently attached to long glycosaminoglycan chains.

Glycosylation occurs mainly in the endoplasmic reticulum and Golgi apparatus, guided by glycosyltransferases that transfer activated sugar donors (e.g., UDP-GlcNAc, CMP-Neu5Ac). The resulting glycoconjugates participate in protein folding, quality control, trafficking, cell-cell adhesion, and receptor signaling.

Abnormal glycosylation is linked to diseases, including congenital disorders of glycosylation and cancer. Glycoconjugates are important in vaccines (glycoconjugate vaccines) and biopharmaceuticals, where glycan structures influence pharmacokinetics and immunogenicity. Proteoglycans in the extracellular matrix regulate tissue hydration and signaling.

Characterization relies on mass spectrometry, chromatography, and lectin-based assays to determine glycan composition and structure.