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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 2cpu

E.C. namealpha-amylase
SpeciesHomo sapiens (Human)
E.C. Number (IntEnz) 3.2.1.1
CSA Homologues of 2cpuThere are 208 Homologs
CSA Entries With UniProtID P04746
CSA Entries With EC Number 3.2.1.1
PDBe Entry 2cpu
PDBSum Entry 2cpu
MACiE Entry 2cpu

Literature Report

IntroductionIn humans, alpha-amylase is present in salivary and pancreatic secretions, and plays a large role in the catalysing the hydrolysis of alpha-1,4-glycosidic linkages in starch.
Human pancreatic alpha-amylase (HPA)is a 496 amino acid single polypeptide chain which binds to esential calcium and chloride ions, and is responsible for the hydrolysis of the partially digested starch (smaller ogliosaccharides) reaching the gut, into glucose.
Inhibition of HPA provides an effective target for the treatment of diabetes.
MechansimHPA catalyses the hydrolysis of 1,4,-glycosidic linkages in the digestion of starch to glucose. This is via a double displacement mechanism involving the formation and hydrolysis of a covalent beta-glycosyl enzyme intermediate.
1. Formation of the intermediate involves attack at the sugar anomeric centre by a nucleopphilic Asp 197 side chain. This is assisted by general acid catalysis of Glu 233 and Asp 300.
2. The covalent glycosyl intermediate undergoes general base catalysed hydrolysis via attack of nucleophilic water at the anomeric centre, again catalysed by Glu 233 and Asp 300. (Glu 233 and Asp 300 side chains deprotonate the water, activating it towards nucleophilic attack). These residues also form hydrogenbonds to the water molecule.
3. This leads to an oxocarbenium ion-like transition state, which goes on to form the deglycosylated product.
Reaction

Catalytic Sites for 2cpu

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
AsnA300315macie:sideChainNucleophilic attack at the sugar anomeric centre is assisted by acid/base catalysis of the anomeric OR' with the Asp side chain. Deprotonation of the nucleophilic water activates it towards attack of the anomeric centre.H bonding to the water molecule also occurs.
Asp 300 also aids the deformation of the substrate and enhances sugar electrophilicity at the anomeric centre.
AspA197212macie:sideChainThe Asp 197 carries out nucleophilic attack on the sugar anomeric centre.
GluA233248macie:sideChainNucleophilic attack at the sugar anomeric centre is assisted by acid/base catalysis of the anomeric OR' with the Glu side chain. Deprotonation of the nucleophilic water activates it towards attack of the anomeric centre.H bonding to the water molecule also occurs.

Literature References

Notes:
Brayer GD
Subsite mapping of the human pancreatic alpha-amylase active site through structural, kinetic, and mutagenesis techniques.
Biochemistry 2000 39 4778-4791
PubMed: 10769135
Rydberg EH
Mechanistic analyses of catalysis in human pancreatic alpha-amylase: detailed kinetic and structural studies of mutants of three conserved carboxylic acids.
Biochemistry 2002 41 4492-4502
PubMed: 11914097
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