Hexokinase I is an enzyme that plays a crucial role in the metabolism of glucose, the primary energy source for cells. It catalyzes the first step of glycolysis, converting glucose into glucose-6-phosphate. This reaction is essential for trapping glucose within the cell and initiating its breakdown for energy production. Hexokinase I is found in various tissues, particularly in the brain and muscle, where energy demand is high. It has a high affinity for glucose, allowing it to function effectively even at low glucose concentrations. This enzyme is part of a larger family of hexokinases, which includes other isoforms like hexokinase II and hexokinase III.