title: CYP83B1, a cytochrome P450 at the metabolic branch point in auxin and indole glucosinolate biosynthesis in Arabidopsis.
abstract: Auxins are growth regulators involved in virtually all aspects of plant development. However, little is known about how plants synthesize these essential compounds. We propose that the level of indole-3-acetic acid is regulated by the flux of indole-3-acetaldoxime through a cytochrome P450, CYP83B1, to the glucosinolate pathway. A T-DNA insertion in the CYP83B1 gene leads to plants with a phenotype that suggests severe auxin overproduction, whereas CYP83B1 overexpression leads to loss of apical dominance typical of auxin deficit. CYP83B1 N-hydroxylates indole-3-acetaldoxime to the corresponding aci-nitro compound, 1-aci-nitro-2-indolyl-ethane, with a K(m) of 3 microM and a turnover number of 53 min(-1). The aci-nitro compound formed reacts non-enzymatically with thiol compounds to produce an N-alkyl-thiohydroximate adduct, the committed precursor of glucosinolates. Thus, indole-3-acetaldoxime is the metabolic branch point between the primary auxin indole-3-acetic acid and indole glucosinolate biosynthesis in Arabidopsis.
authors.affiliation: Departments of Plant Sciences, Molecular and Cellular Biology, and Entomology, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: S
authors.initials: S
authors.lastname: Bak
authors.forename: F E
authors.initials: FE
authors.lastname: Tax
authors.forename: K A
authors.initials: KA
authors.lastname: Feldmann
authors.forename: D W
authors.initials: DW
authors.lastname: Galbraith
authors.forename: R
authors.initials: R
authors.lastname: Feyereisen
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins; D002384:Catalysis; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005961:Glucosinolates / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000096:biosynthesis*; D010105:Oxygenases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D005961:Glucosinolates; D007210:Indoleacetic Acids; D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; C431937:CYP83B1 protein, Arabidopsis