Effect of phosphate concentration on the kinetics of bovine liver glutamate dehydrogenase self-association

The kinetics of the self-association of bovine liver glutamate dehydrogenase was studied at various phosphate buffer concentrations (pH 7.3) at 11.5°C by means of the temperature-jump technique with scattered light detection. The observed relaxation times were well explained by the random association model of Thusius et al. With increasing phosphate concentration, the association rate constant derived from the model decreased, while the dissociation rate constant was left almost constant. Relaxation amplitude was also dependent on the phosphate concentration. The changes in the rate constant and relaxation amplitude with phosphate concentration are well elucidated by assuming that glutamate dehydrogenase is protected from association by specific masking of the association site by phosphate ions.