Effect of Medium pH And Ion Strength on the Thermal Stability of Plant Formate Dehydrogenases

The effect of medium pH and ion strength on the thermal stability of formate dehydrogenases (EC 1.2.1.2, FDH) from model plant Arabidopsis thaliana (AthFDH) and soybean Glycine max (SoyFDH) are studied. The dependence of the residual activity on time is described by the kinetics of the reaction of the first order in all the experimental conditions. The dependence of the first order thermal inactivation constants on phosphate buffer concentration has the form of a bell-shaped curve. It was found that an increase in the pH value resulted in an increase and decrase of inactivation rate constans for SoyFDH and AthFDH, respectively. The activation parameters of the thermal inactivation process, ΔH≠ and ΔS≠ are calculated from the experimental data at different medium pH values and phosphate buffer concentrations.