Hexokinase is the enzyme that phosphorylates glucose to glucose 6-phosphate. It exists in several isoforms or isozymes. One important isoform of hexokinase is glucokinase found in liver and in the beta cells of the pancreas. In the pancreas this enzyme acts as a receptor or sensor to monitor blood glucose concentrations. After a meal, blood glucose rises and activates glucokinase. This signals the release of insulin from the pancreatic beta cells. The circulating insulin can then regulate the uptake of glucose into muscle and adipose tissue.