Journal
FEBS LETTERS
Volume 580, Issue 27, Pages 6384-6390Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.febslet.2006.10.050
Keywords
glutathione-conjugate degradation; monochlorobimane; phytochelatin synthase; vacuolar sequestration
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Monochlorobimane was used as a model xenobiotic for Arabidopsis to directly monitor the compartmentation of glutathione-bimane conjugates in situ and to quantify degradation intermediates in vitro. Vacuolar sequestration of the conjugate was very fast and outcompeted carboxypeptidation to the gamma-glutamylcysteine-bimane intermediate (gamma-EC-B) by phytochelatin synthase (PCS) in the cytosol. Following vacuolar sequestration, degradation proceeded to cysteine-bimane without intermediate. Only co-infiltration of monochlorobimane with Cd(2+) and Cu(2+) increased gamma-EC-B formation to 4% and 25%, respectively, within 60 min. The role of PCS under simultaneous heavy metal stress was confirmed by investigation of different pcs1 null-mutants. In the absence of elevated heavy metal concentrations glutathione-conjugates are therefore first sequestered to the vacuole and subsequently degraded with the initial breakdown step being rate-limiting. (c) 2006 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
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