Effects of pH on the maximal rates of reactions catalyzed by NAD-dependent hydrogenase from Alcaligenes eutrophus

The effects of pH on the maximal rates of the hydrogenase and diaphorase reactions with various accepters catalyzed by NAD-dependent hydrogenase from Alcaligenes eutrophus H16 were studied, The data indicate that at all pH values investigated, the electron transfer to the acceptor is the rate-limiting stage; hence, the reaction rate is essentially determined by the redox properties of the second substrate, The role of the slow conformational changes associated with hydrogenase activation is critical for the patterns of pH profiles of the catalytic activities of the enzyme.