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EC Number

Catalytic Site Atlas

CSA LITERATURE entry for 1auo

E.C. namecarboxylesterase
SpeciesPseudomonas fluorescens (Bacteria)
E.C. Number (IntEnz)
CSA Homologues of 1auo1aur,1fj2,3cn7,3cn9,
CSA Entries With UniProtID Q53547
CSA Entries With EC Number
PDBe Entry 1auo
PDBSum Entry 1auo
MACiE Entry 1auo

Literature Report

IntroductionCarboxylesterases hydrolyse carboxylic ester bonds with relatively broad substrate specificity and are useful for stereospecific synthesis and hydrolysis of esters. The carboxylesterase from Pseudomonas fluorescens shows limited sequence similarity to some members of the alpha/beta hydrolase superfamily, but does have the alpha/beta hydrolase fold.
MechansimCarboxylesterase uses a Ser-His-Asp catalytic triad. Serine, deprotonated by histidine which is stabilised in its charged form by aspartate, carries out a nucleophilic attack on the carbonyl of the substrate. The resulting tetrahedral transition state is stabilised by an oxyanion hole. When it collapses, histidine protonates the leaving group and the result is a covalent enzyme-substrate intermediate. A water molecule, deprotonated by histidine, attacks the covalent intermediate to give another tetrahedral intermediate, which collapses to give the product and the enzyme in its native state.

Catalytic Sites for 1auo

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerA114114macie:sideChainCarries out a nucleophilic attack on the substrate.
HisA199199macie:sideChainGeneral acid/base catalysis
AspA168168macie:sideChainStabilises charged form of histidine.
LeuA2323macie:sideChainForms part of the oxyanion hole to stabilise the transition state.
GlnA115115macie:sideChainForms part of the oxyanion hole to stabilise the transition state.

Literature References

Kim KK
Crystal structure of carboxylesterase from Pseudomonas fluorescens, an alpha/beta hydrolase with broad substrate specificity.
Structure 1997 5 1571-1584
PubMed: 9438866