title: Kinetic and mass spectrometric analyses of the interactions between plant acetohydroxy acid isomeroreductase and thiadiazole derivatives.
abstract: Plant acetohydroxy acid isomeroreductase (EC 1.1.1.86), the second enzyme of the branched chain amino acid biosynthetic pathway, has been submitted to high-throughput screening for herbicide discovery. We report here the discovery of a new class of compounds belonging to the thiadiazole family, which exhibit a strong inhibitory effect on this plant enzyme. Kinetic analyses revealed that these compounds act as either reversible or irreversible noncompetitive inhibitors of the plant enzyme. Reversibility or irreversibility of these compounds can be attributed to the nature of the additional groups of the thiadiazole ring favoring or not favoring the formation of a covalent adduct. Mass spectrometric experiments on the complex between an irreversible compound belonging to the thiadiazole family and the plant enzyme identified Cys498 as the binding site of the inhibitor.
authors.affiliation: Laboratoire Mixte CNRS/Rhône-Poulenc (UMR 41) and Laboratoire de Synthèse Organique, Rhône-Poulenc Agrochimie, 14-20 rue Pierre Baizet, 69263 Lyon Cedex 9, France.
authors.forename: F
authors.initials: F
authors.lastname: Halgand
authors.forename: F
authors.initials: F
authors.lastname: Vives
authors.forename: R
authors.initials: R
authors.lastname: Dumas
authors.forename: V
authors.initials: V
authors.lastname: Biou
authors.forename: J
authors.initials: J
authors.lastname: Andersen
authors.forename: J P
authors.initials: JP
authors.lastname: Andrieu
authors.forename: R
authors.initials: R
authors.lastname: Cantegril
authors.forename: J
authors.initials: J
authors.lastname: Gagnon
authors.forename: R
authors.initials: R
authors.lastname: Douce
authors.forename: E
authors.initials: E
authors.lastname: Forest
authors.forename: D
authors.initials: D
authors.lastname: Job
mesh_terms: D000429:Alcohol Oxidoreductases / Q000037:antagonists & inhibitors / Q000737:chemistry*; D000595:Amino Acid Sequence; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D050540:Ketol-Acid Reductoisomerase; D007700:Kinetics; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010944:Plants / Q000201:enzymology*; D013830:Thiadiazoles / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D013830:Thiadiazoles; D000429:Alcohol Oxidoreductases; D050540:Ketol-Acid Reductoisomerase