Hexokinase
The Pacemaker of Glycolysis

Introduction

The glycolytic reaction       catalyzed by hexokinase

Hexokinase catalyzes the first reaction of glycolysis, the series of reactions that metabolize intracellular glucose. Hexokinase can also break down other hexose sugars and thus has a relatively broad substrate specificity.

Kinases are a common class of enzymes in biochemistry that transfer a phosphoryl group from ATP to their respective substrates. Specifically, hexokinase enhances the nucleophilic attack of the C-6 hydroxyl group of glucose on the gamma phosphate of ATP, forming glucose-6-phosphate (G6P).

As a result of phosphorylation by hexokinase, glucose is committed to a metabolic fate, since negatively-charged G6P is unable to escape across the hydrophobic cell membrane.

As you will see, hexokinase is an obvious example of an induced fit substrate binding mechanism.

Upon binding of a hexose, a large conformational change is observed, where the enzyme clamps down on its substrate for catalysis.