The Enzyme Database

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Accepted name: glucuronosyl-N-acetylglucosaminyl-proteoglycan 4-α-N-acetylglucosaminyltransferase
Reaction: UDP-N-acetyl-D-glucosamine + β-D-glucuronosyl-(1→4)-N-acetyl-α-D-glucosaminyl-proteoglycan = UDP + N-acetyl-α-D-glucosaminyl-(1→4)-β-D-glucuronosyl-(1→4)-N-acetyl-α-D-glucosaminyl-proteoglycan
For diagram of heparan biosynthesis (later stages), click here
Other name(s): α-N-acetylglucosaminyltransferase II glucuronyl-N-acetylglucosaminylproteoglycan α-1,4-N-acetylglucosaminyltransferase
Systematic name: UDP-N-acetyl-D-glucosamine:β-D-glucuronosyl-(1→4)-N-acetyl-α-D-glucosaminyl-proteoglycan 4-α-N-acetylglucosaminyltransferase
Comments: Involved in the biosynthesis of heparin and heparan sulfate. Some forms of the enzyme from human (particularly the enzyme complex encoded by the EXT1 and EXT2 genes) act as bifunctional glycosyltransferases, which also have the 4-β-glucuronosyltransferase (EC, N-acetylglucosaminyl-proteoglycan 4-β-glucuronosyltransferase) activity required for the synthesis of the heparan sulfate disaccharide repeats. Other human forms of this enzyme (e.g. the product of the EXTL1 gene) have only the 4-α-N-acetylglucosaminyltransferase activity. In Caenorhabditis elegans, the product of the rib-2 gene displays the activities of this enzyme as well as EC, glucuronosyl-galactosyl-proteoglycan 4-α-N-acetylglucosaminyltransferase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 336193-98-7
1.  Kim, B.T., Kitagawa, H., Tamura, J., Saito, T., Kusche-Gullberg, M., Lindahl, U. and Sugahara, K. Human tumor suppressor EXT gene family members EXTL1 and EXTL3 encode α1,4-N-acetylglucosaminyltransferases that likely are involved in heparan sulfate/heparin biosynthesis. Proc. Natl. Acad. Sci. USA 98 (2001) 7176–7181. [PMID: 11390981]
2.  Kitagawa, H., Egusa, N., Tamura, J.I., Kusche-Gullberg, M., Lindahl, U. and Sugahara, K. rib-2, a Caenorhabditis elegans homolog of the human tumor suppressor EXT genes encodes a novel α1,4-N-acetylglucosaminyltransferase involved in the biosynthetic initiation and elongation of heparan sulfate. J. Biol. Chem. 276 (2001) 4834–4838. [PMID: 11121397]
3.  Senay, C., Lind, T., Muguruma, K., Tone, Y., Kitagawa, H., Sugahara, K., Lidholt, K., Lindahl, U. and Kusche-Gullberg, M. The EXT1/EXT2 tumor suppressors: catalytic activities and role in heparan sulfate biosynthesis. EMBO Rep. 1 (2000) 282–286. [PMID: 11256613]
4.  Lind, T., Tufaro, F., McCormick, C., Lindahl, U. and Lidholt, K. The putative tumor suppressors EXT1 and EXT2 are glycosyltransferases required for the biosynthesis of heparan sulfate. J. Biol. Chem. 273 (1998) 26265–26268. [PMID: 9756849]
[EC created 2002]

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