Evidence for a Malate Transport into Vacuoles Isolated from Catharanthus roseus Cells

Malate uptake was investigated with vacuoles isolated from Catharanthus roseus cells. The uptake process showed saturation kinetics, was inhibited by organic anions, and was very strongly dependent on the pH of the medium. These data support the classical concept of an anion carrier or channel mechanism and suggest that the Hmal− form was the transported species. Moreover, malate transport was stimulated by the proton gradient across the tonoplast. The H+ translocating enzymes ATPase and PPiase are able to favour malate uptake and, in combination, exert a synergistic effect on this transfer.