ATPase activity associated with vacuoles and tonoplast vesicles isolated from the CAM plant, Kalanchoë daigremontiana

Intact vacuoles were isolated from leaves of the CAM plant, Kalanchoë daigremontiana Hamet et Perr. Both ATPase and acid phosphatase activities were found in the vacuoles. Purified tonoplast vesicles showed only ATPase activity with a pH optimum of 8.0. This activity was Mg2+‐dependent and KCI or NaCI caused a further stimulation. N,N′‐dicyclohexylcarbodiimide, diethylstilbestrol and quercetin inhibited the ATPase almost completely at concentrations well below 1 mM. NaVo3, 1‐ethyl‐3(3‐dimethylaminopropyl)carbodiimide, oligomycin and NaN3 had little or no effect. Carbonyl cyanide m‐chlorophenylhydrazone stimulated the ATPase about 40% at 5 × 10−4M. The Km for ATP was found to be 0.55 mM. These results indicate that the ATPase found in the tonoplast membrane of Kalanchoë daigremontiana is qualitatively similar to that of other plant species.