The Enzyme Database

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EC 2.4.1.135     
Accepted name: galactosylgalactosylxylosylprotein 3-β-glucuronosyltransferase
Reaction: UDP-α-D-glucuronate + [protein]-3-O-(β-D-galactosyl-(1→3)-β-D-galactosyl-(1→4)-β-D-xylosyl)-L-serine = UDP + [protein]-3-O-(β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl)-L-serine
For diagram of heparan and chondroitin biosynthesis (early 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): glucuronosyltransferase I; uridine diphosphate glucuronic acid:acceptor glucuronosyltransferase; UDP-glucuronate:3-β-D-galactosyl-4-β-D-galactosyl-O-β-D-xylosyl-protein D-glucuronosyltransferase; UDP-glucuronate:3-β-D-galactosyl-4-β-D-galactosyl-O-β-D-xylosylprotein D-glucuronosyltransferase
Systematic name: UDP-α-D-glucuronate:[protein]-3-O-(β-D-galactosyl-(1→3)-β-D-galactosyl-(1→4)-β-D-xylosyl)-L-serine D-glucuronosyltransferase (configuration-inverting)
Comments: Involved in the biosynthesis of the linkage region of glycosaminoglycan chains as part of proteoglycan biosynthesis (chondroitin, dermatan and heparan sulfates). Requires Mn2+.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 227184-75-0
References:
1.  Helting, J. and Roden, L. Biosynthesis of chondroitin sulfate. II. Glucuronosyl transfer in the formation of the carbohydrate-protein linkage region. J. Biol. Chem. 244 (1969) 2799–2805. [PMID: 5770003]
2.  Helting, T. Biosynthesis of heparin. Solubilization and partial purification of uridine diphosphate glucuronic acid: acceptor glucuronosyltransferase from mouse mastocytoma. J. Biol. Chem. 247 (1972) 4327–4332. [PMID: 4260846]
3.  Kitagawa, H., Tone, Y., Tamura, J., Neumann, K.W., Ogawa, T., Oka, S., Kawasaki, T. and Sugahara, K. Molecular cloning and expression of glucuronyltransferase I involved in the biosynthesis of the glycosaminoglycan-protein linkage region of proteoglycans. J. Biol. Chem. 273 (1998) 6615–6618. [DOI] [PMID: 9506957]
[EC 2.4.1.135 created 1984, modified 2002, modified 2016]
 
 
EC 2.4.1.174     
Accepted name: glucuronylgalactosylproteoglycan 4-β-N-acetylgalactosaminyltransferase
Reaction: UDP-N-acetyl-α-D-galactosamine + [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-(β-D-GalNAc-(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 chondroitin 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): N-acetylgalactosaminyltransferase I; glucuronylgalactosylproteoglycan β-1,4-N-acetylgalactosaminyltransferase; uridine diphosphoacetylgalactosamine-chondroitin acetylgalactosaminyltransferase I; UDP-N-acetyl-D-galactosamine:D-glucuronyl-1,3-β-D-galactosyl-proteoglycan β-1,4-N-acetylgalactosaminyltransferase; UDP-N-acetyl-D-galactosamine:D-glucuronyl-(1→3)-β-D-galactosyl-proteoglycan 4-β-N-acetylgalactosaminyltransferase
Systematic name: UDP-N-acetyl-D-galactosamine:[protein]-3-O-(β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl)-L-serine 4-β-N-acetylgalactosaminyltransferase (configuration-inverting)
Comments: Requires Mn2+. Involved in the biosynthesis of chondroitin sulfate. Key enzyme activity for the initiation of chondroitin and dermatan sulfates, transferring GalNAc to the GlcA-Gal-Gal-Xyl-Ser core.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 96189-39-8
References:
1.  Rohrmann, K., Niemann, R. and Buddecke, E. Two N-acetylgalactosaminyltransferases are involved in the biosynthesis of chondroitin sulfate. Eur. J. Biochem. 148 (1985) 463–469. [DOI] [PMID: 3922754]
2.  Uyama, T., Kitagawa, H., Tamura, J.-i. and Sugahara, K. Molecular cloning and expression of human chondroitin N-acetylgalactosaminyltransferase: the key enzyme for chain initiation and elongation of chondroitin/dermatan sulfate on the protein linkage region tetrasaccharide shared by heparin/heparan sulfate. J. Biol. Chem. 277 (2002) 8841–8846. [DOI] [PMID: 11788602]
[EC 2.4.1.174 created 1989, modified 2002]
 
 
EC 2.4.1.223     
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 2.4.1.224, 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
References:
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 2.4.1.223 created 2002, modified 2016]
 
 


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