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Vacuolar sequestration of glutathione S ‐conjugates outcompetes a possible degradation of the glutathione moiety by phytochelatin synthase
Author(s) -
Grzam Anke,
Tennstedt Pierre,
Clemens Stephan,
Hell Rüdiger,
Meyer Andreas J.
Publication year - 2006
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2006.10.050
Subject(s) - glutathione , phytochelatin , moiety , chemistry , biochemistry , enzyme , stereochemistry
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 γ‐glutamylcysteine‐bimane intermediate (γ‐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 γ‐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.