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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1cns

E.C. namechitinase
SpeciesHordeum vulgare (Barley)
E.C. Number (IntEnz) 3.2.1.14
CSA Homologues of 1cnsThere are 11 Homologs
CSA Entries With UniProtID P23951
CSA Entries With EC Number 3.2.1.14
PDBe Entry 1cns
PDBSum Entry 1cns
MACiE Entry 1cns

Literature Report

IntroductionThe chitinase enzymes catalyse the hydrolysis of chitin, a biopolyer composed of 1,4 linked N-acetylglucosamine units, a major component of fungal cell walls and insect exoskeletons. The chitinase enzyme collected from barely seeds is a type b member of the class II group. It is used by the seeds to retard fungal growth by interfering with the cell wall.
MechansimInitially, the catalytic site structure had been thought to resemble that of Hen Egg White Lysozyme (HEWL), and adopt a similar mechanism in hydrolysing the 1,4 glycosidic link of chitin. However, more recent investigations have shown chitinase to operate by a different mechanism.
The reaction proceeds through a single displacement mechanism. The general acid, Glu67, protonates the beta-1,4-glycosidic oxygen atom, forming an oxocarbonium ion intermediate. A water molecule, activated by the general base Glu89 attacks the C1 atom of the intermediate state from the alpha side, hydrolytically cleaving the glycosyl bond with inversion of the anomeric position.
Reaction

Catalytic Sites for 1cns

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
GluA6790macie:sideChainThe residue acts as a general acid towards the beta-1,4-glycosidic oxygen atom forming the oxocarbenium intermediate. Through hydrogen bonding interactions the residue facilitates the cleavage of the glycosidic bond.
GluA89112macie:sideChainThe residue acts as a general base towards the hydrolytic water molecule, increasing its nucleophilicity. Molecular dynamics have show the residue to stabilise the carbonium ion intermediate through electrostatic interactions.

Literature References

Notes:
Fukamizo T.
Chitinolytic enzymes: catalysis, substrate binding, and their application.
Curr Protein Pept Sci 2000 1 105-124
PubMed: 12369923
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