Hexokinase

Hexokinase is an essential enzyme that catalyzes the first step in glycolysis, the pathway by which glucose is broken down to produce energy. It converts glucose to glucose-6-phosphate, using ATP as the source of phosphate. This reaction is crucial because it traps glucose within the cell and regulates glucose metabolism based on cellular energy needs. Hexokinase has four isoforms, each with distinct regulatory features and tissue-specific expressions. For example, hexokinase I is ubiquitously present and has a high affinity for glucose, making it active even at low glucose concentrations, while hexokinase IV (glucokinase), found primarily in the liver, acts as a glucose sensor, responding to changes in blood glucose levels.