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Identification of a jasmonate-regulated allene oxide synthase that metabolizes 9-hydroperoxides of linoleic and linolenic acids.
Itoh, Aya; Schilmiller, Anthony L; McCaig, Bonnie C; Howe, Gregg A.
Affiliation
  • Itoh A; Department of Energy Plant Research Laboratory and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1312, USA.
J Biol Chem ; 277(48): 46051-8, 2002 Nov 29.
Article in En | MEDLINE | ID: mdl-12351632
ABSTRACT
Allene oxide synthase (AOS) is a cytochrome P-450 (CYP74A) that catalyzes the first step in the conversion of 13-hydroperoxy linolenic acid to jasmonic acid and related signaling molecules in plants. Here, we report the molecular cloning and characterization of a novel AOS-encoding cDNA (LeAOS3) from Lycopersicon esculentum whose predicted amino acid sequence classifies it as a member of the CYP74C subfamily of enzymes that was hitherto not known to include AOSs. Recombinant LeAOS3 expressed in Escherichia coli showed spectral characteristics of a P-450. The enzyme transformed 9- and 13-hydroperoxides of linoleic and linolenic acid to alpha-ketol, gamma-ketol, and cyclopentenone compounds that arise from spontaneous hydrolysis of unstable allene oxides, indicating that the enzyme is an AOS. Kinetic assays demonstrated that LeAOS3 was approximately 10-fold more active against 9-hydroperoxides than the corresponding 13-isomers. LeAOS3 transcripts accumulated in roots, but were undetectable in aerial parts of mature plants. In contrast to wild-type plants, LeAOS3 expression was undetectable in roots of a tomato mutant that is defective in jasmonic acid signaling. These findings suggest that LeAOS3 plays a role in the metabolism of 9-lipoxygenase-derived hydroperoxides in roots, and that this branch of oxylipin biosynthesis is regulated by the jasmonate signaling cascade.
Subject(s)
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Collection: 01-internacional Database: MEDLINE Main subject: Alpha-Linolenic Acid / Linoleic Acid / Intramolecular Oxidoreductases / Cyclopentanes / Lipid Peroxides Type of study: Diagnostic_studies / Prognostic_studies Language: En Journal: J Biol Chem Year: 2002 Document type: Article Affiliation country: Estados Unidos
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Collection: 01-internacional Database: MEDLINE Main subject: Alpha-Linolenic Acid / Linoleic Acid / Intramolecular Oxidoreductases / Cyclopentanes / Lipid Peroxides Type of study: Diagnostic_studies / Prognostic_studies Language: En Journal: J Biol Chem Year: 2002 Document type: Article Affiliation country: Estados Unidos