Abstract
The mechanisms of saccharose and sorbitol transport in Prunus persica leaves were investigated in plasma membrane vesicles purified by aqueous 2-phase partitioning and equilibrated in pH 7.5 buffer containing K+. The imposition of an artificial proton motive force energized an active uptake of both saccharose and sorbitol. The maximum uptake rate of saccharose was 2.5 times higher than that of sorbitol. Saccharose and sorbitol uptake exhibited saturation kinetics suggesting they were carrier-mediated. Apparent Km for the saccharose and the sorbitol uptake were 0.36 and 0.67 mM, respectively. Active absorption of saccharose was completely inhibited by a non-permeant thiol reagent, PCMBS, contrary to sorbitol absorption. These results suggested that saccharose and sorbitol were transported at least by two different carriers.
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