Kinetic evidence for a ‘mnemonical’ mechanism for rat liver glucokinase

Abstract

Inhibition studies of glucokinase were carried out with the products of the reaction, G-6-P and MgADP-, as well as with ADP3-, Mg2+ and ATP4-. The results of these, together with those of kinetic studies of the uninhibited reaction described previously indicate that the enzyme obeys a ''mnemonical'' mechanism. This implies that the co-operativity observed with glucose as substrate arises because glucose binds differentially to 2 forms of the free enzyme that are not in equilibrium under steady-state conditions. The mechanism predicts the decrease in glucose co-operativity observed at low concentrations of MgATP2-. The product-inhibition results suggest that G-6-P is released first and that it is possibly displaced by MgATP2- in a concerted reaction.