Hexokinase, EC 2.7.1.1

published: 21 Nov 2011 (14:08)

About Hexokinases

Hexokinases are group of enzymes of transferase family (EC 2.7.1.1), with very wide range of molecular weight, from 40 to 120kDa, that catalyze transfer of phosphate group from ATP molecule to D-glucose or other D-hexoses. The overall reaction can be written as ATP + D-hexose = ADP + D-hexose 6-phosphate. This enzyme is very important because it involved into glycolysis cycle at the first step of converting of α-D-glucose.

Systematic name for hexokinase is ATP:D-hexose 6-phosphotransferase, but in literature can be used under the different names: hexokinase D, hexokinase (phosphorylating), hexokinase type IV glucokinase, ATP-dependent hexokinase, glucose ATP phosphotransferase, hexokinase type I, hexokinase type II, hexokinase type III and hexokinase type IV.

Open and Closed glucokinase conformations

Open (left; pdb code 1V4T) and closed (right; pdb code 1V4S) conformations of human glucokinase. Protein surface is coloured according to the protein atom chargers.

Hexokinase comprised from two domains, which can adopt open and closed conformations. In the free enzyme the cleft between two domains is widely open. Glucose, or glucose-6-phosphate binding process cause the closure two domains for catalytic act.

In closed conformation of hexokinase, or glucokinase, the substrate is completely buried by protein atoms.

Hexokinase IUBMB Enzyme Nomenclature hierarchy

Hexokinase classification on the basis of recommendations of Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB):

EC 2 Transferases
- EC 2.7 Transferring phosphorus-containing groups
  - EC 2.7.1 Phosphotransferases with an alcohol group as acceptor
    - EC 2.7.1.1 ATP:D-hexose 6-phosphotransferase

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