Effect of pH on the Hydrogenase Activity of Desulfovibrio vulgaris

Intact hydrogenase in Desulfovibrio vulgaris (Hildenborough) cells exhibits catalytic activity for the reaction H 2 +M ox ⇔2H + +M red (here M ox /M red is a redox couple serving as an electron acceptor/donor). Dependence on pH of the catalytic activity was studied in view of the expected pH dependence of the substrate concentration [H + ] and the standard free energy change of the overall reaction Δ G °. It has been revealed that the conventional Michaelis‐Menten type analysis for the H 2 evolution reaction leads an erroneous conclusion with respect to the dependence of the reaction rate on [H + ] and that the pH dependence of the hydrogenae‐catalyzed H 2 evolution and consumption reactions reflect the pH‐dependent change of Δ G °.