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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1g6t

E.C. name3-phosphoshikimate 1-carboxyvinyltransferase
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz) 2.5.1.19
CSA Homologues of 1g6tThere are 20 Homologs
CSA Entries With UniProtID P0A6D3
CSA Entries With EC Number 2.5.1.19
PDBe Entry 1g6t
PDBSum Entry 1g6t
MACiE Entry 1g6t

Literature Report

IntroductionEnolpyruvylshikimate 3-phosphate synthase (EPSP synthase) catalyses the sixth step in aromatic amino acid biosynthesis in bacteria, plants and some parasites. It forms EPSP from shikimate 3-phosphate and phospho-enolpyruvate in an addition/elimination reaction the proceeds through a tetrahedral intermediate. Because this biosynthetic pathway is absent in animals, the enzyme is a potential antibacterial target with knock-out strains being avirulent.
MechansimAn aspartate residue deprotonates the 5-OH of the shikimate 3-phosphate, activating the oxygen to attack at the C2 of phospho-enolpyruvate with concomitant protonation at C3 by Glu341. A tetrahedral intermediate is formed. Glu341 is then thought to act as a general base at C3, initiating the collapse of the intermediate, elimination of phosphate and the formation of enolpyruvylshikimate 3-phosphate.
The most recent work suggests a hybrid acid/base- electrostatic reaction, with catalytic residues optimised for acid/base and electrostatic roles. Glu341 is thought to act as both a general acid, protonating C3 in the addition step, and a general base, deprotonating C3 in the elimination step while also stabilising the cationic intermediate. This is achieved by the formation of an electrostatic 'sandwich' with Asp313.
While earlier work implicates Lys22 as a general acid/base, mutagenesis and kinetics suggests the residue's main role is in substrate binding.
Reaction

Catalytic Sites for 1g6t

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
GluA341341macie:sideChainThe residue acts as both a general acid and general base throughout the reaction, first donating a proton to the C3 of the enolpyruvyl-phosphate in the elimination step, and then abstracting a proton from C3 in the elimination step. This has been shown by stereo-chemical analysis, mutagenesis and structure determination. The residue is also thought to drive the reaction by stabilising the cationic intermediate in an electrostatic sandwich, and so lower the reaction barrier. The position of the side chain is influenced by hydrogen bonds to Lys411 and His385 through the residue's backbone amide.
GluA341341macie:mainChainAmideThe residue acts as both a general acid and general base throughout the reaction, first donating a proton to the C3 of the enolpyruvyl-phosphate in the elimination step, and then abstracting a proton from C3 in the elimination step. This has been shown by stereo-chemical analysis, mutagenesis and structure determination. The residue is also thought to drive the reaction by stabilising the cationic intermediate in an electrostatic sandwich, and so lower the reaction barrier. The position of the side chain is influenced by hydrogen bonds to Lys411 and His385 through the residue's backbone amide.
AspA313313macie:sideChainThe carboxylic side group is thought to activate the 5-OH of shikimate 3-phosphate towards attack at the C2 of phospho-enolpyruvate by proton abstraction. It is also positioned to stabilise the cationic intermediate, forming an electrostatic 'sandwich' with the close proximity Glu341.
LysA411411macie:sideChainThe residue's side chain is implicated in aligning the side chain of Glu341 for catalytic activity.
HisA385385macie:sideChainThe residue's side chain is implicated in aligning the side chain of Glu341 for catalytic activity.

Literature References

Notes:
Berti PJ
Catalytic residues and an electrostatic sandwich that promote enolpyruvyl shikimate 3-phosphate synthase (AroA) catalysis.
Biochemistry 2009 48 3699-3707
PubMed: 19271774
Schönbrunn E
Interaction of the herbicide glyphosate with its target enzyme 5-enolpyruvylshikimate 3-phosphate synthase in atomic detail.
Proc Natl Acad Sci U S A 2001 98 1376-1380
PubMed: 11171958
de Souza AX
5-Enolpyruvylshikimate-3-phosphate synthase: determination of the protonation state of active site residues by the semiempirical method.
Bioorg Chem 2008 36 113-120
PubMed: 18325563
Eschenburg S
A new view of the mechanisms of UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) and 5-enolpyruvylshikimate-3-phosphate synthase (AroA) derived from X-ray structures of their tetrahedral reaction intermediate states.
J Biol Chem 2003 278 49215-49222
PubMed: 13129913
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