Glycosyltransferases (abbre. GTFs, Gtfs) are enzymes (EC 2.4) that are responsible for the biosynthesis of disaccharides, oligosaccharides and polysaccharides. They catalyse the transfer of monosaccharide moieties from activated nucleotide sugar (also known as the "glycosyl donor") to a glycosyl acceptor molecule, usually an alcohol.
The result of glycosyl transfer can be a carbohydrate, glycoside, oligosaccharide, or a polysaccharide. Some glycosyltransferases catalyse transfer to inorganic phosphate or water. Glycosyl transfer can also occur to protein residues, usually to tyrosine, serine, or threonine to give O-linked glycoproteins, or to asparagine to give N-linked glycoproteins. Mannosyl groups may be transferred to tryptophan to generate C-mannosyl tryptophan, which is relatively abundant in eukaryotes. Transferases may also use lipids as an acceptor, forming glycolipids, or even lipid-linked sugar phosphate donors, such as dolichol phosphates.
It is common that sugar nucleotide derivatives are used as glycosyl d