InterPro domain: IPR003406

The biosynthesis of disaccharides, oligosaccharides and polysaccharides involves the action of hundreds of different glycosyltransferases. These enzymes catalyse the transfer of sugar moieties from activated donor molecules to specific acceptor molecules, forming glycosidic bonds. A classification of glycosyltransferases using nucleotide diphospho-sugar, nucleotide monophospho-sugar and sugar phosphates ([intenz:2.4.1.-]) and related proteins into distinct sequence based families has been described [ 1 ]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site. The same three-dimensional fold is expected to occur within each of the families. Because 3-D structures are better conserved than sequences, several of the families defined on the basis of sequence similarities may have similar 3-D structures and therefore form 'clans'.

This is the glycosyltransferase family 14 GT14 , a family of two different beta-1,6-N-acetylglucosaminyltransferase enzymes, I-branching enzyme ( 2.4.1.150 ) and core-2 branching enzyme ( 2.4.1.102 ). I-branching enzyme, an integral membrane protein, converts linear into branched poly-N-acetyllactosaminoglycans in the glycosylation pathway, and is responsible for the production of the blood group I-antigen during embryonic development [ 2 ]. Core-2 branching enzyme, also an integral membrane protein, forms crucial side-chain branches in O-glycans in the glycosylation pathway [ 3 ].

1. A classification of nucleotide-diphospho-sugar glycosyltransferases based on amino acid sequence similarities. Biochem. J. 326 ( Pt 3), 929-39
2. Expression of the developmental I antigen by a cloned human cDNA encoding a member of a beta-1,6-N-acetylglucosaminyltransferase gene family. Genes Dev. 7, 468-78
3. Molecular cloning and expression of a novel beta-1, 6-N-acetylglucosaminyltransferase that forms core 2, core 4, and I branches. J. Biol. Chem. 274, 3215-21