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Catalytic Site Atlas Search Results
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Catalytic Site Atlas

CSA LITERATURE entry for 1esc

E.C. nameESTERASE
SpeciesStreptomyces scabies (Streptomyces scabiei)
E.C. Number (IntEnz) 3.1.1.-
CSA Homologues of 1esc1esd,1ese,
CSA Entries With UniProtID
CSA Entries With EC Number 3.1.1.-
PDBe Entry 1esc
PDBSum Entry 1esc
MACiE Entry 1esc

Literature Report

IntroductionThis esterase enzyme is secreted by the bacterium Streptomyces scabies, a causal agent of the potato scab decease. Invasion into the plant host is brought about by the liplytic action of the secreted esterase, which is presumed to hydrolyse specific ester bonds within the suberin lipid which covers the plant tubers. Although the esterase possesses a catalytic triad similar to that of other serine hydrolases, the structure remains unique among known proteins. It is the first example of a naturally occurring enzyme in which a neutral hydrogen bond acceptor, a main chain carbonyl, replaces a carboxylic acid within the triad.
MechansimA nucleophilic residue attacks at the substrate carbonyl, forming a tetrahedral intermediate (the anionic transition state being stabilised by an oxyanion hole). This collapses to give an acyl-enzyme intermediate, which is hydrolysed to yield the free residue and substrate.

Catalytic Sites for 1esc

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerA1453macie:sideChainThe residue acts as a nucleophile towards the ester substrate, forming a tetrahedral intermediate. The hydroxyl group hydrogen bonds to the His 283, which then acts as a base to deprotonate the residue, enhancing its nucleophilic character. The residue's backbone amide is implicated in forming an oxyanion hole, lowering the energy of the anionic transition state.
SerA1453macie:mainChainAmideThe residue acts as a nucleophile towards the ester substrate, forming a tetrahedral intermediate. The hydroxyl group hydrogen bonds to the His 283, which then acts as a base to deprotonate the residue, enhancing its nucleophilic character. The residue's backbone amide is implicated in forming an oxyanion hole, lowering the energy of the anionic transition state.
HisA283322macie:sideChainThe residue forms a neutral hydrogen bond with the backbone carbonyl of Typ 280, which enhances its basic character towards the nucleophilic Ser 14 and controls the residue's orientation within the active site. This is a unique example of a neutral hydrogen bond in the absence of a carboxylic acid group among the serine hydrolase enzymes. The residue is also hydrogen bonded to Ser 14, and donates a proton to the anionic transition state, regaining neutrality within the active site.
TrpA280319macie:mainChainAmidehe residue backbone carbonyl hydrogen bonds to the His 283, directing the residues orientation within the active site and effecting its pKa.
AsnA106145macie:sideChainThe residue is implicated in forming an oxyanion hole which stabilises the anionic tetrahedral transition state formed in hydrolysis.
GlyA66105macie:mainChainAmideThe residue is implicated in forming an oxyanion hole which stabilises the anionic tetrahedral transition state formed in hydrolysis.

Literature References

Notes:
Hale VA
Mutational analysis of the Streptomyces scabies esterase signal peptide.
Appl Microbiol Biotechnol 1996 45 189-198
PubMed: 8920191
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