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3.5.1.1 Phosphorylation of Glucose
Glucose enters into the glycolytic pathway by phosphorylation to glucose 6- phosphate, accomplished by the enzyme hexokinase. However, in liver parenchyma cells and in pancreatic islet cells, this function is carried out by glucokinase. ATP is required as phosphate donor, and it reacts as the Mg-ATP complex. Hexokinase Glucose + ATP →glucose 6- phosphate The terminal high-energy phosphate of ATP is utilized, and ADP is produced. The reaction is accompanied by considerable loss of free energy as heat and therefore, under physiologic conditions, may be regarded as irreversible.
Hexokinase is inhibited in an allosteric manner by the product, glucose 6- phosphate. The function of glucokinase is to remove glucose from the blood following digestion and absorption. It is specific for glucose. |
Last modified: Tuesday, 21 February 2012, 9:40 AM