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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1b73

E.C. nameglutamate racemase
SpeciesAquifex pyrophilus (Bacteria)
E.C. Number (IntEnz) 5.1.1.3
CSA Homologues of 1b73There are 22 Homologs
CSA Entries With UniProtID P56868
CSA Entries With EC Number 5.1.1.3
PDBe Entry 1b73
PDBSum Entry 1b73
MACiE Entry M0001

Literature Report

IntroductionGlutamate racemase is responsible for the synthesis of D-glutamate, an essential building block of peptidoglycan, found in bacterial cell walls where it provides structural integrity. Due to its uniqueness to bacteria, peptidoglycan and enzymes involved in its biosynthesis have been considered as attractive targets for designing new antibacterial drugs. Peptidoglycan is formed from a repeating unit of a disaccharide, N-acetylglucosamine and N-acetylmuramic acid to which a small group of amino acids consisting of L-alanine, D-alaline, D-glutamate and either lysine or diaminopimelic acid are covalently attached. The presence of D-amino acids presumably protect the cell wall from proteases which can only recognise the L-isomer.
MechansimIn the most likely scenario, a two base mechanism, Cys70 and Cys178 are responsible for the deprotonation and protonation of the C-alpha atom of D-Glucose, respectively. Cys70 deprotonates the C-alpha to form a carbanion intermediate before Cys178 reprotonates on the opposite side of the C-alpha to produce L-Glucose. The carboxylates of Asp7 and Glu147 are also important in catalysis - a possible role could be to assist the thiols in bringing about the proton transfer steps although simply substrate binding is more likely. Alternatively, it is possible that the racemisation reaction may proceed by a concerted mechanism in which a penta-coordinated carbon is formed in the transition state.
Reaction

Catalytic Sites for 1b73

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerA88macie:sideChain
AspA77macie:sideChain
CysA178178macie:sideChain
CysA7070macie:sideChain

Literature References

Notes:
Hwang KY
Structure and mechanism of glutamate racemase from Aquifex pyrophilus.
Nat Struct Biol 1999 6 422-426
PubMed: 10331867
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