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Catalytic Site Atlas

CSA LITERATURE entry for 1qd6

E.C. namephospholipase A1
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz) 3.1.1.32
CSA Homologues of 1qd61fw2,1fw3,1ild,1ilz,1im0,1qd5,
CSA Entries With UniProtID P0A921
CSA Entries With EC Number 3.1.1.32
PDBe Entry 1qd6
PDBSum Entry 1qd6
MACiE Entry 1qd6

Literature Report

IntroductionThe outer membrane phospholipase A(OMPLA) is an integral membrane enzyme present in the outer membrane of Gram-negative bacteria. It catalyses the hydrolysis of acylester bonds in phospholipids. The physiological function of OMPLA is still not known.
MechansimThe mechanism of OMPLA is analogous to that of serine hydrolases. His142 acts as a base to deprotonate the side chain of Ser144 to allow its nucleophilic attack on the ester bond. The tetrahedral transition state is stabilised by an oxyanion hole formed by the amide of Gly146 and 2 water molecules. His142 protonates the leaving group and then deprotonates a water molecule to allow its nucleophilic attack on the acylenzyme intermediate. The essential Ca2+ ion increases the nucleophilicity of the serine and polarises the ester carbonyl bond to facilitate the nucleophilic attack. It is also involved in the oxyanion stabilisation.
Reaction

Catalytic Sites for 1qd6

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
GlyD146166macie:mainChainAmideIts amide group forms the oxyanion hole to stabilise the transition state.
HisC142162macie:sideChainIt deprotonates Ser 144 to allow its nucleophilic attack on the ester bond. It protonates the leaving group. It activates a water molecule to regenerate the enzyme from the acylenzyme intermediate.
SerC144164macie:sideChainIt acts as a nucleophile to attack the ester bond of the substrate.

Annotated By Reference To The Literature - Site 2 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
GlyC146166macie:mainChainAmideIts amide group forms the oxyanion hole to stabilise the transition state.
HisD142162macie:sideChainIt deprotonates Ser 144 to allow its nucleophilic attack on the ester bond. It protonates the leaving group. It activates a water molecule to regenerate the enzyme from the acylenzyme intermediate.
SerD144164macie:sideChainIt acts as a nucleophile to attack the ester bond of the substrate.

Literature References

Notes:
Brok RG
A conserved histidine residue of Escherichia coli outer-membrane phospholipase A is important for activity.
Eur J Biochem 1995 234 934-938
PubMed: 8575454
Horrevoets AJ
Inactivation of Escherichia coli outer-membrane phospholipase A by the affinity label hexadecanesulfonyl fluoride. Evidence for an active-site serine.
Eur J Biochem 1991 198 247-253
PubMed: 2040286
Brok RG
Escherichia coli outer membrane phospholipase A: role of two serines in enzymatic activity.
Biochemistry 1996 35 7787-7793
PubMed: 8672479
Snijder HJ
Structural evidence for dimerization-regulated activation of an integral membrane phospholipase.
Nature 1999 401 717-721
PubMed: 10537112
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