Cglycosyltransferases

C-glycosyltransferases, also written as C glycosyltransferases, are a specialized class of glycosyltransferases that catalyze the formation of carbon–carbon glycosidic bonds between a sugar donor and a carbon atom of an acceptor molecule. This contrasts with the more common O- and N-glycosyltransferases, which form glycosidic bonds to oxygen or nitrogen atoms.

Donors are activated sugars, frequently UDP-sugars or similar nucleotide-sugar donors, while acceptors are often aromatic or heterocyclic compounds such as flavonoids, phenolics, or antibiotics. The resulting C-glycosides are typically more resistant to hydrolysis and oxidation because C–C linkages are chemically robust.

Biochemical roles for CGTs have been demonstrated in plants, bacteria, and fungi, where they participate in the biosynthesis of natural products, including C-glycosylated flavonoids and other secondary metabolites. The exact mechanisms and catalytic strategies vary among CGTs, but many rely on specialized active-site residues to enable direct carbon–carbon bond formation; some systems may involve metal ions or cofactors.

From a biotechnological perspective, CGTs are of interest for the engineered synthesis of C-glycosides with improved pharmacokinetic properties. Research in this area focuses on characterizing substrate scope, improving stability and expression, and expanding donor and acceptor compatibility. CGTs are catalogued within the broader CAZy classification of glycosyltransferases, illustrating their relation to other sugar-transfer enzymes while highlighting their unique C-glycosylation activity.