Dimerization of Brain Hexokinase Induced by Its Regulator Glucose 6-Phosphate

Bovine brain mitochondrial hexokinase type I, undergoes a concentration-dependent dimerization in presence of its product inhibitor glucose 6-phosphate. The effectiveness of this ligand in inducing the aggregation of brain hexokinase closely parallels its kinetic behavior as an inhibitor of this enzyme. ATP and inorganic phosphate known to antagonize the inhibitory effect of glucose 6-phosphate also cause a reversal of this dimerization process. ADP, another inhibitor of brain hexokinase, however, has no effect on the sedimentation behavior of the enzyme. It is suggested that the conformational alteration underlying the formation of hexokinase dimer in presence of glucose 6-phosphate has physiological significance.