title: gamma-Glutamyl transpeptidase GGT4 initiates vacuolar degradation of glutathione S-conjugates in Arabidopsis.
abstract: The xenobiotic monochlorobimane is conjugated to glutathione in the cytosol of Arabidopsis thaliana, transported to the vacuole, and hydrolyzed to cysteine S-bimane [Grzam, A., Tennstedt, P., Clemens, S., Hell, R. and Meyer, A.J. (2006) Vacuolar sequestration of glutathione S-conjugates outcompetes a possible degradation of the glutathione moiety by phytochelatin synthase. FEBS Lett. 580, 6384-6390]. The work here identifies gamma-glutamyl transpeptidase 4 (At4g29210, GGT4) as the first step of vacuolar degradation of glutathione conjugates. Hydrolysis of glutathione S-bimane is blocked in ggt4 null mutants of A. thaliana. Accumulation of glutathione S-bimane in mutants and in wild-type plants treated with the high affinity GGT inhibitor acivicin shows that GGT4 is required to initiate the two step hydrolysis sequence. GGT4:green fluorescent protein fusions were used to demonstrate that GGT4 is localized in the lumen of the vacuole.
authors.affiliation: Heidelberg Institute of Plant Sciences, University of Heidelberg, Im Neuenheimer Feld 360, Heidelberg, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Grzam
authors.forename: Melinda N
authors.initials: MN
authors.lastname: Martin
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Hell
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Meyer
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000502:physiology; D001483:Base Sequence; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D005978:Glutathione / Q000031:analogs & derivatives* / Q000378:metabolism*; D007555:Isoxazoles / Q000494:pharmacology; D050217:Metabolic Detoxication, Phase II; D016254:Mutagenesis, Insertional; D011499:Protein Processing, Post-Translational; D014617:Vacuoles / Q000378:metabolism*; D005723:gamma-Glutamyltransferase / Q000235:genetics / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D007555:Isoxazoles; D005723:gamma-Glutamyltransferase; D005978:Glutathione; C006303:acivicin