The presence of multiple hexokinase isozymes (i-iv) for the phosphorylation of glucose enables specific organs to regulate carbohydrate metabolism in a unique way. hexokinase iv (blue curve in the plot below), also called glucokinase, is the predominant isozyme in liver and has distinct kinetic properties from the other hexokinase isozymes (representative curve in red). note the difference in the shapes of the curves within the physiological range of glucose concentration (~4 to 6 mm).