Reaction: UDP-N-acetyl-α-D-glucosamine + β-D-Gal-(1→4)-β-D-GlcNAc-(1→3)-β-D-Gal-(1→4)-β-D-GlcNAc-R = UDP + β-D-Gal-(1→4)-β-D-GlcNAc-(1→3)-[β-D-GlcNAc-(1→6)]-β-D-Gal-(1→4)-β-D-GlcNAc-R
Glossary: β-D-galactosyl-(1→4)-N-acetyl-D-glucosaminyl-R = type 2 precursor disaccharide
Other name(s): GCNT2 (gene name); GCNT3 (gene name); IGnT; I-branching β1,6-N-acetylglucosaminyltransferase; N-acetylglucosaminyltransferase; uridine diphosphoacetylglucosamine-acetyllactosaminide β1→6-acetylglucosaminyltransferase; Galβ1→4GlcNAc-R β1→6 N-acetylglucosaminyltransferase; UDP-N-acetyl-D-glucosamine:β-D-galactosyl-1,4-N-acetyl-D-glucosaminide β-1,6-N-acetyl-D-glucosaminyltransferase
Systematic name: UDP-N-acetyl-α-D-glucosamine:β-D-galactosyl-(1→4)-N-acetyl-β-D-glucosaminyl-(1→3)-β-D-galactosyl-(1→4)-N-acetyl-β-D-glucosaminide 6-β-N-acetylglucosaminyltransferase (configuration-inverting)
Comments: The enzyme acts on poly-N-acetyllactosamine [glycan chains of β-D-galactosyl-(1→4)-N-acetyl-D-glucosamine units connected by β(1,3) linkages] attached to proteins or lipids. It transfers a GlcNAc residue by β(1,6)-linkage to galactosyl residues close to non-reducing terminals, introducing a branching pattern known as I branching.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 85638-40-0
References:
1. Van den Eijnden, D.H., Winterwerp, H., Smeeman, P. and Schiphorst, W.E.C.M. Novikoff ascites tumor cells contain N-acetyllactosaminide β1→3 and β1→6 N-acetylglucosaminyltransferase activity. J. Biol. Chem. 258 (1983) 3435-3437. [PMID: 6219989]
2. Basu, M. and Basu, S. Biosynthesis in vitro of Ii core glycosphingolipids from neolactotetraosylceramide by β 1-3- and β 1-6-N-acetylglucosaminyltransferases from mouse T-lymphoma. J. Biol. Chem. 259 (1984) 12557-12562. [PMID: 6238026]
3. Piller, F., Cartron, J.P., Maranduba, A., Veyrieres, A., Leroy, Y. and Fournet, B. Biosynthesis of blood group I antigens. Identification of a UDP-GlcNAc:GlcNAc β 1-3Gal(-R) β 1-6(GlcNAc to Gal) N-acetylglucosaminyltransferase in hog gastric mucosa. J. Biol. Chem. 259 (1984) 13385-13390. [PMID: 6490658]
4. Bierhuizen, M.F., Maemura, K., Kudo, S. and Fukuda, M. Genomic organization of core 2 and I branching β-1,6-N-acetylglucosaminyltransferases. Implication for evolution of the β-1,6-N-acetylglucosaminyltransferase gene family. Glycobiology 5 (1995) 417-425. [PMID: 7579796]
5. Ujita, M., McAuliffe, J., Suzuki, M., Hindsgaul, O., Clausen, H., Fukuda, M.N. and Fukuda, M. Regulation of I-branched poly-N-acetyllactosamine synthesis. Concerted actions by I-extension enzyme, I-branching enzyme, and β1,4-galactosyltransferase I. J. Biol. Chem. 274 (1999) 9296-9304. [PMID: 10092606]
6. Yeh, J.C., Ong, E. and Fukuda, M. Molecular cloning and expression of a novel β-1, 6-N-acetylglucosaminyltransferase that forms core 2, core 4, and I branches. J. Biol. Chem. 274 (1999) 3215-3221. [PMID: 9915862]