Glutathione in its oxidized form (GSSG) is rapidly taken up into isolated barley vacuoles, while uptake of reduced glutathione (GSH) is only marginal. GSSG transport is strictly ATP-dependent and is a saturable process (K m 0.4 to 0.6 mм). Uptake is inhibited by vanadate, but not by bafilomycin, a specific inhibitor of the vacuolar H + -ATPase. The observation that i) the non-hydrolysable ATP analogue adenylylim idodiphosphate does not stimulate, but rather inhibits the ATP-dependent uptake of GSSG and ii) that a four-fold accumulation of GSSG is observed in the presence of bafilomycin, suggests that GSSG is transported into the vacuole by a primary active process similar to that of glutathione S-conjugates (E. Martinoia, E. Grill, R. Tommasini, K. Kreuz, N. Amrhein, Nature 364, 247-249 (1993)). U ptake of GSSG is competitively inhibited by the glutathione S-conjugate of the herbicide m etolachlor (K i 80 μм), indicating that transport of GSSG is mediated by the glutathione S-conjugate ATPase.
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Tommasini et al. (1993) studied this question.