title: Linolenate 9R-dioxygenase and allene oxide synthase activities of Lasiodiplodia theobromae.
abstract: Jasmonic acid (JA) is synthesized from linolenic acid (18:3n-3) by sequential action of 13-lipoxygenase, allene oxide synthase (AOS), and allene oxide cyclase. The fungus Lasiodiplodia theobromae can produce large amounts of JA and was recently reported to form the JA precursor 12-oxophytodienoic acid. The objective of our study was to characterize the fatty acid dioxygenase activities of this fungus. Two strains of L. theobromae with low JA secretion (~0.2 mg/L medium) oxygenated 18:3n-3 to 5,8-dihydroxy-9Z,12Z,15Z-octadecatrienoic acid as well as 9R-hydroperoxy-10E,12Z,15Z-octadecatrienoic acid, which was metabolized by an AOS activity into 9-hydroxy-10-oxo-12Z,15Z-octadecadienoic acid. Analogous conversions were observed with linoleic acid (18:2n-6). Studies using [11S-(2)H]18:2n-6 revealed that the putative 9R-dioxygenase catalyzed stereospecific removal of the 11R hydrogen followed by suprafacial attack of dioxygen at C-9. Mycelia from these strains of L. theobromae contained 18:2n-6 as the major polyunsaturated acid but lacked 18:3n-3. A third strain with a high secretion of JA (~200 mg/L) contained 18:3n-3 as a major fatty acid and produced 5,8-dihydroxy-9Z,12Z,15Z-octadecatrienoic acid from added 18:3n-3. This strain also lacked the JA biosynthetic enzymes present in higher plants.
authors: Department of Pharmaceutical Biosciences, Uppsala Biomedical Center, Uppsala University, P.O. Box 591, 75124 Uppsala, Sweden.
authors: Fredrik
authors: F
authors: Jernerén
authors: Felipe
authors: F
authors: Eng
authors: Mats
authors: M
authors: Hamberg
authors: Ernst H
authors: EH
authors: Oliw
mesh_terms: D001203:Ascomycota / Q000201:enzymology*; D056148:Chromatography, Reverse-Phase; D003517:Cyclopentanes / Q000378:metabolism*; D049308:Dioxygenases / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D019746:Intramolecular Oxidoreductases / Q000378:metabolism*; D019787:Linoleic Acid / Q000378:metabolism; D050356:Lipid Metabolism; D008084:Lipoxygenase / Q000378:metabolism; D025282:Mycelium / Q000201:enzymology*; D054883:Oxylipins / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000096:biosynthesis*; D010944:Plants / Q000382:microbiology; D053719:Tandem Mass Spectrometry; D017962:alpha-Linolenic Acid / Q000378:metabolism
chemical_list: D003517:Cyclopentanes; D005231:Fatty Acids, Unsaturated; D054883:Oxylipins; D010937:Plant Growth Regulators; C495366:hydroxyoctadecadienoic acid; D017962:alpha-Linolenic Acid; C027369:octadecadienoic acid; C011006:jasmonic acid; D019787:Linoleic Acid; C117433:13-lipoxygenase; D049308:Dioxygenases; D008084:Lipoxygenase; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase