The effect of salts on malate dehydrogenase from leaves of Zea mays

The effect of sodium and potassium chlorides and of sodium sulphate on malic dehydrogenase (EC 1.1.1.37) from Zea mays chloroplasts and cytosol has been investigated. Optimal NaCl concentration (100 mM) doubled the rate of oxaloacetate reduction by the cytosolic enzyme with NADH but caused an increase of some IO-fold with NADPH. Oxidation of malate was also stimulated using NADP but the optimal concentration was less than 20 mM. The chloroplast enzyme activity [with NAD(H)] was not significantly activated by increasing ionic strength.