In the first reaction of glycolysis, the gama-phosphoryl group of an ATP molecule is transferred to the oxygen at the C-6 of glucose (magnesium ion is required as the reactive form of ATP is the chelated complex with magnesium (II) ion). This step is a direct nucleophilic attack of the hydroxyl group on the terminal phosphoryl group of the ATP molecule (Aleshin, 99). This produces glucose-6-phosphate and ADP. Hexokinase is the enzyme that catalyzes this phosphoryl-group-transfer. Hexokinase undergoes and induced-fit conformational change when it binds to glucose, which ultimately prevents the hydrolysis of ATP. It is also allosterically inhibited by physiological concentrations of its immediate product, glucose-6-phosphate. This is a mechanism by which the influx of substrate into the glycolytic pathway is controlled.
Glycolysis is a sequence of 10 enzyme-catalyzed reactions by which glucose is converted to pyruvate. Most of the enzymes found in this pathway are present in all living species. Moreover, they are found in the cytosol of the cells, and the conversion of one molecule of glucose to two molecules of pyruvate is also accompanied by the net conversion two molecules of ADP to two molecules of ATP. In addition to the two molecules of ATP produced, two molecules of NAD+ are reduced to NADH. In multicellular organisms, this pathway is found in all differentiated cell types.
[Colleges & Dept's] [Chemistry Dept.] [Chem 406]