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Catalytic Site Atlas Search Results
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Catalytic Site Atlas

CSA LITERATURE entry for 1tht

E.C. nameTHIOESTERASE
SpeciesVibrio harveyi (Bacteria)
E.C. Number (IntEnz) 2.3.1.-
CSA Homologues of 1tht
CSA Entries With UniProtID
CSA Entries With EC Number 2.3.1.-
PDBe Entry 1tht
PDBSum Entry 1tht
MACiE Entry 1tht

Literature Report

IntroductionMyristoyl acyl carrier protein specific thioesterase (C14ACP-TE) is a lux-specific acyltransferase belonging to the alpha/beta hydrolase family. The acyl transferase is part of the fatty acid reductase system required for aldehyde biosynthesis. It produces fatty acids for the light-emitting reaction catalysed by luciferase in luminescent bacteria. In Vibrio harveyi, C14ACP-TE is responsible for catalysing the transfer or hydrolysis of acyl group from either myristoyl-ACP or myristoyl-CoA to form myristic acid, and for diverting the myristic acid to the bioluminescence pathway, where it undergoes NADPH-dependent reduction and subsequent FMNH2- and O2-dependent oxidation of the corresponding aldehyde, with accompanying emission of light.
MechansimEnzymatic hydrolysis of the thioester bond proceeds using the catalytic triad of Ser114, Asp211, and His241. His241 activates Ser114 as a nucleophile by abstracting a proton from the serine hydroxyl as the carbonyl carbon of the substrate is attacked by the nucleophile. This results in the formation of a tetrahedral transition state which collapses, with the His241 donating a proton to the first leaving group (the acyl-carrier protein), to form the acylenzyme intermediate. The intermediate is subsequently cleaved by a hydrolytic water molecule. The water is activated by proton abstraction by the His residue and attacks nucleophilically the central carbonyl atom of the acylenzyme ester bond, forming a tetrahedral intermediate, which collapses, resulting in the release of the product, myristic acid, and regeneration of the enzyme active site.

Catalytic Sites for 1tht

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerA114114macie:sideChainSer114 is activated by His241. It acts as a nucleophile and attacks the substrate to form the acylenzyme intermediate. Its backbone amide may also be involved in the formation of an oxyanion hole.
SerA114114macie:mainChainAmideSer114 is activated by His241. It acts as a nucleophile and attacks the substrate to form the acylenzyme intermediate. Its backbone amide may also be involved in the formation of an oxyanion hole.
HisA241241macie:sideChainHis241 acts as a general acid/base catalyst, activating Ser114 and water as nucleophiles.

Annotated By Reference To The Literature - Site 2 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerB114114macie:sideChainSer114 is activated by His241. It acts as a nucleophile and attacks the substrate to form the acylenzyme intermediate. Its backbone amide may also be involved in the formation of an oxyanion hole.
SerB114114macie:mainChainAmideSer114 is activated by His241. It acts as a nucleophile and attacks the substrate to form the acylenzyme intermediate. Its backbone amide may also be involved in the formation of an oxyanion hole.
HisB241241macie:sideChainHis241 acts as a general acid/base catalyst, activating Ser114 and water as nucleophiles.

Literature References

Notes:Asp is not essential in catalysis, nor does there appear to be any direct evidence for its involvement in the mechanism. It seems that Asp has a stabilisation role relative to His.
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