title: Cytosolic γ-glutamyl peptidases process glutathione conjugates in the biosynthesis of glucosinolates and camalexin in Arabidopsis.
abstract: The defense-related plant metabolites known as glucosinolates play important roles in agriculture, ecology, and human health. Despite an advanced biochemical understanding of the glucosinolate pathway, the source of the reduced sulfur atom in the core glucosinolate structure remains unknown. Recent evidence has pointed toward GSH, which would require further involvement of a GSH conjugate processing enzyme. In this article, we show that an Arabidopsis thaliana mutant impaired in the production of the γ-glutamyl peptidases GGP1 and GGP3 has altered glucosinolate levels and accumulates up to 10 related GSH conjugates. We also show that the double mutant is impaired in the production of camalexin and accumulates high amounts of the camalexin intermediate GS-IAN upon induction. In addition, we demonstrate that the cellular and subcellular localization of GGP1 and GGP3 matches that of known glucosinolate and camalexin enzymes. Finally, we show that the purified recombinant GGPs can metabolize at least nine of the 10 glucosinolate-related GSH conjugates as well as GS-IAN. Our results demonstrate that GSH is the sulfur donor in the biosynthesis of glucosinolates and establish an in vivo function for the only known cytosolic plant γ-glutamyl peptidases, namely, the processing of GSH conjugates in the glucosinolate and camalexin pathways.
authors.affiliation: Section for Molecular Plant Biology, Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, 1871 Frederiksberg, Denmark.
authors.forename: Fernando
authors.initials: F
authors.lastname: Geu-Flores
authors.forename: Morten Emil
authors.initials: ME
authors.lastname: Møldrup
authors.forename: Christoph
authors.initials: C
authors.lastname: Böttcher
authors.forename: Carl Erik
authors.initials: CE
authors.lastname: Olsen
authors.forename: Dierk
authors.initials: D
authors.lastname: Scheel
authors.forename: Barbara Ann
authors.initials: BA
authors.lastname: Halkier
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology*; D005961:Glucosinolates / Q000096:biosynthesis*; D005978:Glutathione / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007211:Indoles / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism*; D000094162:Phytoalexins
chemical_list: D029681:Arabidopsis Proteins; D005961:Glucosinolates; D005978:Glutathione; D007211:Indoles; D010447:Peptide Hydrolases; D011993:Recombinant Fusion Proteins; D013455:Sulfur; D013844:Thiazoles; C102405:camalexin; D000094162:Phytoalexins