Kinetics of rat liver glucokinase. Co-operative interactions with glucose at physiologically significant concentrations.

The kinetics of glucokinase from rat liver were studied over wide ranges of glucose and MgATP2- concentrations. The initial rate shows a co-operative dependence on the glucose concentration, with Hill coefficients in the range 1.2-1.5. The degree of glucose co-operativity increases with the MgATP2- concentration, but no co-operativity was detected for the dependence of the rate on the MgATP2- concentration. The effects observed occur at physiologically reasonable concentrations of glucose and MgATP2- and are consistent with the presumed function of glucokinase in maintaining a constant concentration of glucose in the blood.