title: A fungal catalase reacts selectively with the 13S fatty acid hydroperoxide products of the adjacent lipoxygenase gene and exhibits 13S-hydroperoxide-dependent peroxidase activity.
abstract: The genome of the fungal plant pathogen Fusarium graminearum harbors six catalases, one of which has the sequence characteristics of a fatty acid peroxide-metabolizing catalase. We cloned and expressed this hemoprotein (designated as Fg-cat) along with its immediate neighbor, a 13S-lipoxygenase (cf. Brodhun et al., PloS One, e64919, 2013) that we considered might supply a fatty acid hydroperoxide substrate. Indeed, Fg-cat reacts abruptly with the 13S-hydroperoxide of linoleic acid (13S-HPODE) with an initial rate of 700-1300s-1. By comparison there was no reaction with 9R- or 9S-HPODEs and extremely weak reaction with 13R-HPODE (~0.5% of the rate with 13S-HPODE). Although we considered Fg-cat as a candidate for the allene oxide synthase of the jasmonate pathway in fungi, the main product formed from 13S-HPODE was identified by UV, MS, and NMR as 9-oxo-10E-12,13-cis-epoxy-octadecenoic acid (with no traces of AOS activity). The corresponding analog is formed from the 13S-hydroperoxide of α-linolenic acid along with novel diepoxy-ketones and two C13 aldehyde derivatives, the reaction mechanisms of which are proposed. In a peroxidase assay monitoring the oxidation of ABTS, Fg-cat exhibited robust activity (kcat 550s-1) using the 13S-hydroperoxy-C18fatty acids as the oxidizing co-substrate. There was no detectable peroxidase activity using the corresponding 9S-hydroperoxides, nor with t-butyl hydroperoxide, and very weak activity with H2O2or cumene hydroperoxide at micromolar concentrations of Fg-cat. Fg-cat and the associated lipoxygenase gene are present together in fungal genera Fusarium, Metarhizium and Fonsecaea and appear to constitute a partnership for oxidations in fungal metabolism or defense.
authors.affiliation: Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA. Electronic address: tarvi.teder@ttu.ee.
authors.forename: Tarvi
authors.initials: T
authors.lastname: Teder
authors.affiliation: Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA. Electronic address: william.boeglin@vanderbilt.edu.
authors.forename: William E
authors.initials: WE
authors.lastname: Boeglin
authors.affiliation: Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA. Electronic address: claus.schneider@vanderbilt.edu.
authors.forename: Claus
authors.initials: C
authors.lastname: Schneider
authors.affiliation: Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA. Electronic address: alan.brash@vanderbilt.edu.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Brash
mesh_terms: D002374:Catalase / Q000378:metabolism*; D003517:Cyclopentanes / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D019746:Intramolecular Oxidoreductases / Q000378:metabolism; D019787:Linoleic Acid / Q000378:metabolism; D008054:Lipid Peroxides / Q000378:metabolism; D008084:Lipoxygenase / Q000378:metabolism*; D009829:Oleic Acids / Q000378:metabolism; D010084:Oxidation-Reduction; D054883:Oxylipins / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism*; D013237:Stereoisomerism; D015003:Yeasts / Q000378:metabolism*; D020122:tert-Butylhydroperoxide / Q000378:metabolism
chemical_list: D003517:Cyclopentanes; D005227:Fatty Acids; D005656:Fungal Proteins; D008054:Lipid Peroxides; D009829:Oleic Acids; D054883:Oxylipins; C037352:13-octadecenoic acid; C011006:jasmonic acid; D020122:tert-Butylhydroperoxide; D019787:Linoleic Acid; D006861:Hydrogen Peroxide; D002374:Catalase; D009195:Peroxidase; C117433:13-lipoxygenase; D008084:Lipoxygenase; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase
keywords: ABTS assay; Catalase; Fusarium; HPODE; Lipoxygenase; NMR; Peroxidase