Transport of Oxidized Glutathione into Barley Vacuoles: Evidence for the Involvement of the Glutathione-S-Conjugate ATPase

Abstract

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 ATPdependent and is a saturable process (Km 0.4 to 0.6 mM). 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 adenylylimidodiphosphate 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)). Uptake of GSSG is competitively inhibited by the glutathione S-conjugate of the herbicide metolachlor (K1 80βm), indicating that transport of GSSG is mediated by the glutathione S-conjugate ATPase. © 1993, Walter de Gruyter. All rights reserved.