Influence of Ion Strength and pH on Thermal Stability of Yeast Formate Dehydrogenase

Abstract

The kinetics of the thermal inactivation of recombinant wild–type formate dehydrogenase from Candida boidinii yeast was studied in the temperature range of 53–61oC and pH 6.0, 7.0, and 8.0. It was shown that the loss of the enzyme’s activity proceeds via a monomolecular mechanism. Activation parameters ∆Н­ and ∆S­ were calculated based on the temperature relations dependence of inactivation rate constants according to the transition state theory. Both parameters are in a range that corresponds to globular protein denaturation processes. Optimal conditions for the stability of the enzyme were high concentrations of the phosphate buffer or of the enzyme substrate sodium formate at pH = 7.0.

Characterization of a novel thermotolerant NAD+-dependent formate dehydrogenase from hot climate plant cotton (Gossypium hirsutum L.)

“…The pH of the medium affects the catalytic activity of the enzyme due to the altered ionization of the charged groups in the protein globule. Even a single group's ionization can cause conformational changes in the protein (Tishkov et al 2010). Here, the K m of GhFDH1 at pH 9 is lower than the K m at pH 8, whereas k cat did not change at different pHs (pH 6-9); it is thought that the substrate binding affinity changed according to the medium pH and pKa values of the ionizable groups of amino acids.…”