•Mammals possess several molecular forms of hexokinase.•Different molecular forms of an enzyme catalyzing the same reaction are called isoenzymes, isozymes, or isoforms. •Most tissues express hexokinase I, II, or III,all low KMenzymes.•Because intracellular glucose levels (2–15 mM) are usually far higher than the KM value for hexokinase, the enzyme often functions in vivo at saturating substrate concentrations.•A low affinity isozyme of hexokinase IV in liver with a sigmoidal dependence on glucose concentration permits that organ to adjust glucose utilization to glucose supply at high blood glucose levels.Glucokinase (葡萄糖激酶)