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Catalytic Site Atlas

CSA LITERATURE entry for 1b6t

E.C. namepantetheine-phosphate adenylyltransferase
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz) 2.7.7.3
CSA Homologues of 1b6t
CSA Entries With UniProtID P0A6I6
CSA Entries With EC Number 2.7.7.3
PDBe Entry 1b6t
PDBSum Entry 1b6t
MACiE Entry M0299

Literature Report

IntroductionPhosphopantetheine adenylyltransferase (PPAT), isolated from Escherichia coli, catalyses the magnesium-dependent adenylyl transfer from ATP to 4'-phosphopantetheine (Ppant or PhP) to form dephospho-CoA (dPCoA). This reaction is the penultimate step in the synthesis of CoA. PPAT belongs to the nucleotidyltransferase alpha/beta phosphodiesterase superfamily, whose members catalyse the transfer of a nucleotide monophosphate to a substrate by stabilising the transition state of the reaction.
PPAT is a hexamer consisting of two trimers. While each subunit possesses an active site, it appears that only the subunits of one trimer will catalyse the reaction at a given time. The reaction proceeds via a random bi-bi mechanism in that the order of the binding of ATP and Ppant is not fixed, nor is the release of dPCoA and pyrophosphate. CoA can regulate the activity of PPAT by binding to the PPAT.PPi complex, thus preventing the binding of a new Ppant substrate molecule.
MechansimOne of the 4'-phosphate oxygens of Ppant undergoes nucleophilic attack on the alpha-phosphate group of ATP with pyrophosphate as the leaving group. The pentacovalent transition state is stabilised by His18 while the leaving group is stabilised by Arg91, Ser129 and the magnesium ion.
Reaction

Catalytic Sites for 1b6t

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
HisA1818macie:sideChainHis18 stabilises the pentacovalent transition state by forming a hydrogen bond to the non-ester oxygens of P(alpha).
SerA129129macie:mainChainAmideSer129 stabilises the beta-phosphate, making pyrophosphate a better leaving group.
ArgA9191macie:sideChainArg91 stabilises the beta-phosphate, making pyrophosphate a better leaving group.

Annotated By Reference To The Literature - Site 2 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
HisB1818macie:sideChainHis18 stabilises the pentacovalent transition state by forming a hydrogen bond to the non-ester oxygens of P(alpha).
SerB129129macie:mainChainAmideSer129 stabilises the beta-phosphate, making pyrophosphate a better leaving group.
ArgB9191macie:sideChainArg91 stabilises the beta-phosphate, making pyrophosphate a better leaving group.

Literature References

Notes:
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