Hexokinase I is an enzyme that plays a crucial role in glucose metabolism. It catalyzes the phosphorylation of glucose to form glucose-6-phosphate, which is the first step in the process of breaking down glucose for energy. This reaction is essential for cellular respiration and energy production in various tissues. Hexokinase I is primarily found in the brain and muscle tissues, where it helps regulate blood sugar levels. It has a high affinity for glucose, allowing it to effectively capture and process glucose even at low concentrations. This makes it vital for maintaining energy supply in cells, especially during periods of high demand.