Characterization of the H Translocating Adenosine Triphosphatase and Pyrophosphatase of Vacuolar Membranes Isolated by Means of a Perfusion Technique from Chara corallina

Abstract

Sealed tonoplast vesicles were isolated from single cells of Chara corallina with the aid of an intracellular perfusion technique in combination with a 3/10% Percoll two step gradient centrifugation. The isolated tonoplast fraction was free from plasmalemma and chloroplasts, and showed no activities of cytochrome c oxidase, and latent IDPase, but had about 10% of the NADH-cytochrome c reductase activity. The vesicles had both ATPase and PPase activities, which could be stimulated in the presence of 10 micromolar gramicidin by 170 and 130%, respectively, demonstrating the existence of sealed vesicles. Furthermore, ATP- and PPi-dependent H(+) pumping through the membrane into the vesicles was shown. Both ATPase and PPase had pH optima around pH 8.5. At the physiological pH, 7.3, they still had more than 80% of their maximal activities. Ammonium molybdate, azide, and vanadate had no or little effect on the activities of both enzymes or their associated H(+) pumping activities. N,N'-dicyclohexylcarbodiimide inhibited the ATPase strongly (I(50) = 20 micromolar) but the PPase only weakly. The ATPase was also more sensitive to N-ethylmaleimide than the PPase. 4,4'-Stilbenedisulfonic acid affected both enzyme activities and their associated H(+) pumping activities. This is in contrast to the H(+)-PPase of higher plants which is 4,4'-stilbenedisulfonic acid insensitive.