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Catalytic Site Atlas

CSA LITERATURE entry for 1xvt

E.C. nameCROTONOBETAINYL-COA:CARNITINE COA-TRANSFERASE
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz) 2.8.3.-
CSA Homologues of 1xvtThere are 32 Homologs
CSA Entries With UniProtID
CSA Entries With EC Number 2.8.3.-
PDBe Entry 1xvt
PDBSum Entry 1xvt
MACiE Entry 1xvt

Literature Report

IntroductionThe enzymes required for the metabolism of L-carnitine in E. Coli is encoded by the cai operon. CaiB, a class III CoA transferase, catalyses the transfer of the CoA group from crotonobetainyl-CoA to L-carnitine.
MechansimAsp 169 is nucleophilic and attacks the carbonyl carbon of the crotonobetainyl-CoA thioester group. This displaces the coenzyme A thiolate, although it is not certain if this is by an addition-elimination mechanism with tetrahedral intermediate, or by an SN2 mechanism with a tetrahedral transition state (this applies to all the steps in the mechanism).
The carboxylate group of carnitine is nucleophilic and attacks the gamma-carbon of the Asp 169 side chain (now forming an anhydride with the crotonobetaine group). This displaces the crotonobetaine product and forms a new anhydride intermediate.
The CoA thiolate attacks the carbonyl group of the carnitine moiety, displacing and regenerating Asp 169 and forming the carnitine-CoA product.

Catalytic Sites for 1xvt

Annotated By Reference To The Literature - Site 2 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
AspA169169macie:sideChainAsp 169 acts as a nucleophilic catalyst. It displaces the CoA thiolate from crotonobetainyl-CoA and remains acylated in the anhydride intermediates.

Literature References

Notes:
Rangarajan ES
Crystal structure of Escherichia coli crotonobetainyl-CoA: carnitine CoA-transferase (CaiB) and its complexes with CoA and carnitinyl-CoA.
Biochemistry 2005 44 5728-5738
PubMed: 15823031
Jonsson S
Kinetic and mechanistic characterization of the formyl-CoA transferase from Oxalobacter formigenes.
J Biol Chem 2004 279 36003-36012
PubMed: 15213226
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