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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1aql

E.C. namesterol esterase
SpeciesBos taurus (Bovine)
E.C. Number (IntEnz) 3.1.1.13
CSA Homologues of 1aql1akn,1f6w,1jmy,2bce,
CSA Entries With UniProtID P30122
CSA Entries With EC Number 3.1.1.13
PDBe Entry 1aql
PDBSum Entry 1aql
MACiE Entry 1aql

Literature Report

IntroductionBile salt-activated lipase (BAL) is one of two lipases secreted from the vertebrate pancreas into the intestine for the digestion of fat. In a few mammals, BAL is also present in the milk to facilitate fat absorption in infants. Because of its wide range of substrate reactivities, BAL has been documented with several different names, including pancreatic carboxylester lipase, pancreatic cholesterol esterase, triacylglycerol lipase and lysophospholipase. There is evidence to support the importance of BAL for the absorption of cholesterol, vitamin A and triacylglycerol. The hydrolytic activity of BAL on naturally occurring lipids requires the presence of bile salt.
MechansimBAL utilises a Ser/His/Asp catalytic triad to hydrolyse an ester bond by nucleophilic substitution. The reaction has two stages – in the first, an enzyme-substrate bond is formed and in the second it is hydrolysed by water.
Reaction

Catalytic Sites for 1aql

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerA194212macie:sideChainCarries out a nucleophilic attack on the substrate.
HisA435453macie:sideChainDeprotonates serine to activate it as a nucleophile.
AspA320338macie:sideChainStabilises charges on His435.
GlyA107125macie:mainChainAmideForms part of the oxyanion hole to stabilise the negatively charged transition state.
AlaA108126macie:mainChainAmideForms part of the oxyanion hole to stabilise the negatively charged transition state.
AlaA195213macie:mainChainAmideForms part of the oxyanion hole to stabilise the negatively charged transition state.

Literature References

Notes:
Wang X
The crystal structure of bovine bile salt activated lipase: insights into the bile salt activation mechanism.
Structure 1997 5 1209-1218
PubMed: 9331420
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