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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1moq

E.C. nameglutamine---fructose-6-phosphate transaminase (isomerizing)
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz) 2.6.1.16
CSA Homologues of 1moqThere are 22 Homologs
CSA Entries With UniProtID P17169
CSA Entries With EC Number 2.6.1.16
PDBe Entry 1moq
PDBSum Entry 1moq
MACiE Entry M0082

Literature Report

Introduction Glucosamine-fructose-6-phosphate aminotransferase (isomerizing) also known as Glucosamine-6-phosphate synthase (GlmS), catalyses the first reaction in hexamine biosynthesis. It belongs to an F-type group of glutamine-dependent amidotransferase family of enzymes, which utilise the glutamine amide nitrogen in the biosynthesis of phosphoribosylamine, glutamate or asparagine.
The enzyme consists of two structural domains, an N-terminal glutaminase domain, which hydrolyses glutamine to glutamate and ammonia (residues 1-240), and a C-terminal isomerase domain (residues 241-608), which catalyses the ketose-aldose isomerisation and utilises the nitrogen for synthesis of GlcN-6P.
The isomerase domain is responsible for two activities of GlmS, the conversion of Fru-6P into GlcN-6P in the presence of glutamine (the synthase activity), and the isomerisation of Fru-6P into Glc-6P (the phosphoglucose isomerase - like activity) in the absence of glutamine.
The product of the reaction with fructose 6-phosphate, glucosamine 6-phosphate, undergoes transformation leading towards formation of uridine diphospho-N-acetylglucosamine - which is a precursor to all amino sugar-containing macromolecules. Much interest has been shown in this enzyme that is believed to have important implications in antibacterial/antifungal therapy and diabetes treatment.
Mechansim The sugar phosphate isomerisation involves a ring opening step catalysed by HIS 504 and an enolisation step with GLU 488 catalysing the hydrogen transfer from C1 to C2 of the substrate. The enediol intermediate is stabilised by a helix dipole and the amino group of LYS 603. GLU 481 and LYS 485 are strictly conserved may play a role in deprotonating the hydroxyl of the intermediate.
Reaction

Catalytic Sites for 1moq

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
LysA603604macie:sideChain
LysA485486macie:sideChain
GluA488489macie:sideChain
GluA481482macie:sideChain

Literature References

Notes:
Obmolova G.
Crystallization and preliminary X-ray analysis of the two domains of glucosamine-6-phosphate synthase from Escherichia coli
J Mol Biol 1994 242 703-705
PubMed: 7932726
Teplyakov A
The mechanism of sugar phosphate isomerization by glucosamine 6-phosphate synthase.
Protein Sci 1999 8 596-602
PubMed: 10091662
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