Does a proton-pumping ATPase exist in the tonoplast?
In order to account for the accumulation of metabolites in plant vacuoles, the existence of a proton-pumping ATPase has been widely suggested in the literature. The demonstration of such a tonoplast-bound ATPase was merely based on the characterization of a nitrate-sensitive microsomal fraction. In some examples, this ATPase activity has been evidenced on vacuole preparations obtained under conditions which were criticized by Boller. The application of the reverse phase high-performance liquid chromatography method (RP-HPLC) to the simultaneous separation of adenine nucleotides, in the presence of tonoplast vesicles isolated from Catharanthus roseus, showed results not necessarily correlated with the ATPase hypothesis. Moreover, in light of the H+-quenching of quinacrine fluorescence observed during ATP hydrolysis by vacuoles or tonoplast vesicles, the existence of a proton-pumping ATPase may be questioned.[1]References
- Does a proton-pumping ATPase exist in the tonoplast? Dupaix, A., Hill, M., Volfin, P., Arrio, B. Biochimie (1986) [Pubmed]
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