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Catalytic Site Atlas

CSA LITERATURE entry for 1jqn

E.C. namephosphoenolpyruvate carboxylase
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz) 4.1.1.31
CSA Homologues of 1jqn1fiy,1jqo,1qb4,
CSA Entries With UniProtID P00864
CSA Entries With EC Number 4.1.1.31
PDBe Entry 1jqn
PDBSum Entry 1jqn
MACiE Entry 1jqn

Literature Report

IntroductionPhosphoenolpyruvate carboxylase (PEPC) catalyses the irreversible carboxylation of phosphoenolpyruvate (PEP) to form oxaloacetate (OAA) and Pi using divalent Mg or Mn as a cofactor. The active species for initial carboxylation is not CO2 but the chemically less reactive bicarbonate anion, which dominates in the cytoplasm where PEPC functions. The enzyme is present in all photosynthetic organisms, including higher plants, green algae, cyanobacteria and photosynthetic bacteria, and most nonphotosynthetic bacteria and protozoa, but is notably absent from animals, fungi, and yeasts. PEPC primarily plays an anaplerotic role by replenishing C4-dicarboxylic acids utilised for both energy and biosynthetic metabolisms. 1jqn is a crystal structure of a PEPC from E. Coli with Mn2+.
MechansimThe first chemical step in the proposed mechanism is the nucleophilic attack by bicarbonate to form carboxyphosphate and enolate of pyruvate. In order to make the phosphorus atom less negative, the positively charged electrostatic pocket formed by Arg396, Arg699, and Arg713 allows the dissipation of the negative charges of the phosphate group during the approach. In the second chemical step of the proposed mechanism His138 acts as a base to abstract a proton from carboxyphosphate; CO2 is generated, the hydrophobic environment in the active site pocket may stabilize the CO2 liberated from the carboxyphosphate. Finally the carbon dioxide generated is nucleophilically attacked by enolate of pyruvate to generate oxaloacetate. The phosphate anion abstracts a proton from His138 to form a phosphate group.
Reaction

Catalytic Sites for 1jqn

Literature References

Notes:Not Arg587 just serves to bind to ligands and hence is not catalytic by our definition.
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