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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1ig8

E.C. namehexokinase
SpeciesSaccharomyces cerevisiae (Baker's yeast)
E.C. Number (IntEnz) 2.7.1.1
CSA Homologues of 1ig81bdg,2nzt,3b8a,
CSA Entries With UniProtID P04807
CSA Entries With EC Number 2.7.1.1
PDBe Entry 1ig8
PDBSum Entry 1ig8
MACiE Entry 1ig8

Literature Report

IntroductionYeast Hexokinase PII is one of the two isoenzymes present in S. cerevisiae which are able to catalyse the phosphorylation of glucose to glucose-6-phosphate. This is the first step in glycolysis, so is of vital importance as it creates an intermediate which can be passed into many other pathways such as glycogen synthesis and the pentose phosphate pathway. 80% sequence identity is observed between the isoenzymes, and both show significant structural identity to the mammalian form of the enzyme, allowing them to be placed together in the same homologous family.
MechansimThe reaction proceeds via an SN2 mechanism with the 6C OH of the glucose acting as a nucleophile, due to deprotonation by Asp 211, to attack the gamma phosphate of ATP. In doing so the position of glucose in the binding site changes to bring it within optimum hydrogen bonding distance of Ser 158, thus stabilising the reaction's transition state. The pentavalent phosphate is stabilised by electrostatic interactions with Lys 173's positively charged side chain.
Reaction

Catalytic Sites for 1ig8

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
AspA211211macie:sideChainDeprotonates glucose's 6OH group to allow it to act as a nucleophile and attack the gamma phosphate of ATP leading to an SN2 reaction.
SerA158158macie:sideChainStabilises transition state by binding to the 3OH of glucose when it is making a nucleophilic attack on the gamma phosphate
ArgA173173macie:sideChainContacts the gamma phosphate of ATP thus is able to stabilise the pentavalent phosphate transition state through electrostatic interactions.

Literature References

Notes:
Arora KK
Glucose phosphorylation. Site-directed mutations which impair the catalytic function of hexokinase.
J Biol Chem 1991 266 5359-5362
PubMed: 2005085
Kuser PR
The high resolution crystal structure of yeast hexokinase PII with the correct primary sequence provides new insights into its mechanism of action.
J Biol Chem 2000 275 20814-20821
PubMed: 10749890
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