The Enzyme Database

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Accepted name: glucuronosyl-galactosyl-proteoglycan 4-α-N-acetylglucosaminyltransferase
Reaction: UDP-N-acetyl-α-D-glucosamine + [protein]-3-O-(β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl)-L-serine = UDP + [protein]-3-O-(α-D-GlcNAc-(1→4)-β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl)-L-serine
For diagram of heparan biosynthesis (later stages), click here
Glossary: [protein]-3-O-(β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl)-L-serine = [protein]-3-O-(β-D-glucuronosyl-(1→3)-β-D-galactosyl-(1→3)-β-D-galactosyl-(1→4)-β-D-xylosyl)-L-serine
Other name(s): α-N-acetylglucosaminyltransferase I; α1,4-N-acetylglucosaminyltransferase; glucuronosylgalactosyl-proteoglycan 4-α-N-acetylglucosaminyltransferase; UDP-N-acetyl-D-glucosamine:β-D-glucuronosyl-(1→3)-β-D-galactosyl-(1→3)-β-D-galactosyl-(1→4)-β-D-xylosyl-proteoglycan 4IV-α-N-acetyl-D-glucosaminyltransferase; glucuronyl-galactosyl-proteoglycan 4-α-N-acetylglucosaminyltransferase
Systematic name: UDP-N-acetyl-α-D-glucosamine:[protein]-3-O-(β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl)-L-serine 4IV-α-N-acetyl-D-glucosaminyltransferase (configuration-retaining)
Comments: Enzyme involved in the initiation of heparin and heparan sulfate synthesis, transferring GlcNAc to the (GlcA-Gal-Gal-Xyl-)Ser core. Apparently products of both the human EXTL2 and EXTL3 genes can catalyse this reaction. In Caenorhabditis elegans, the product of the rib-2 gene displays this activity as well as that of EC, glucuronosyl-N-acetylglucosaminyl-proteoglycan 4-α-N-acetylglucosaminyltransferase. For explanation of the use of a superscript in the systematic name, see 2-Carb-37.2.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 179241-74-8
1.  Kitagawa, H., Shimakawa, H. and Sugahara, K. The tumor suppressor EXT-like gene EXTL2 encodes an α1,4-N-acetylhexosaminyltransferase that transfers N-acetylgalactosamine and N-acetylglucosamine to the common glycosaminoglycan-protein linkage region. The key enzyme for the chain initiation of heparan sulfate. J. Biol. Chem. 274 (1999) 13933–13937. [DOI] [PMID: 10318803]
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. [DOI] [PMID: 11121397]
[EC created 2002, modified 2016]

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