Reaction: (1) UDP-α-N-acetyl-D-glucosamine + β-D-glucuronosyl-(1→3)-N-acetyl-β-D-glucosaminyl-(1→4)-[nascent hyaluronan] = UDP + N-acetyl-β-D-glucosaminyl-(1→4)-β-D-glucuronosyl-(1→3)-N-acetyl-β-D-glucosaminyl-(1→4)-[nascent hyaluronan]
(2) UDP-α-D-glucuronate + N-acetyl-β-D-glucosaminyl-(1→4)-β-D-glucuronosyl-(1→3)-[nascent hyaluronan] = UDP + β-D-glucuronosyl-(1→3)-N-acetyl-β-D-glucosaminyl-(1→4)-β-D-glucuronosyl-(1→3)-[nascent hyaluronan]
For diagram click here.
Glossary: GlcNAc = N-acetyl-D-glucosamine
GlcA = glucuronic acid
Other name(s): spHAS; seHAS
Systematic name: Alternating UDP-α-N-acetyl-D-glucosamine:β-D-glucuronosyl-(1→3)-[nascent hyaluronan] 4-N-acetyl-β-D-glucosaminyltransferase and UDP-α-D-glucuronate:N-acetyl-β-D-glucosaminyl-(1→4)-[nascent hyaluronan] 3-β-D-glucuronosyltransferase
Comments: The enzyme from Streptococcus Group A and Group C requires Mg2+. The enzyme adds GlcNAc to nascent hyaluronan when the non-reducing end is GlcA, but it adds GlcA when the non-reducing end is GlcNAc . The enzyme is highly specific for UDP-GlcNAc and UDP-GlcA; no copolymerization is observed if either is replaced by UDP-Glc, UDP-Gal, UDP-GalNAc or UDP-GalA. Similar enzymes have been found in a variety of organisms.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 39346-43-5
1. DeAngelis, P.L., Papaconstantinou, J. and Weigel, P.H. Molecular cloning, identification and sequence of the hyaluronan synthase gene from Group A Streptococcus pyogenes. J. Biol. Chem. 268 (1993) 19181-19184. [PMID: 8366070]
2. Jing, W. and DeAngelis, P.L. Dissection of the two transferase activities of the Pasteurella multocida hyaluronan synthase: two active sites exist in one polypeptide. Glycobiology 10 (2000) 883-889. [PMID: 10988250]
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