title: Lipoxygenase-catalyzed transformation of epoxy fatty acids to hydroxy-endoperoxides: a potential P450 and lipoxygenase interaction.
abstract: Herein, we characterize a generally applicable transformation of fatty acid epoxides by lipoxygenase (LOX) enzymes that results in the formation of a five-membered endoperoxide ring in the end product. We demonstrated this transformation using soybean LOX-1 in the metabolism of 15,16-epoxy-α-linolenic acid, and murine platelet-type 12-LOX and human 15-LOX-1 in the metabolism of 14,15-epoxyeicosatrienoic acid (14,15-EET). A detailed examination of the transformation of the two enantiomers of 15,16-epoxy-α-linolenic acid by soybean LOX-1 revealed that the expected primary product, a 13S-hydroperoxy-15,16-epoxide, underwent a nonenzymatic transformation in buffer into a new derivative that was purified by HPLC and identified by UV, LC-MS, and ¹H-NMR as a 13,15-endoperoxy-16-hydroxy-octadeca-9,11-dienoic acid. The configuration of the endoperoxide (cis or trans side chains) depended on the steric relationship of the new hydroperoxy moiety to the enantiomeric configuration of the fatty acid epoxide. The reaction mechanism involves intramolecular nucleophilic substitution (SNi) between the hydroperoxy (nucleophile) and epoxy group (electrophile). Equivalent transformations were documented in metabolism of the enantiomers of 14,15-EET by the two mammalian LOX enzymes, 15-LOX-1 and platelet-type 12-LOX. We conclude that this type of transformation could occur naturally with the co-occurrence of LOX and cytochrome P450 or peroxygenase enzymes, and it could also contribute to the complexity of products formed in the autoxidation reactions of polyunsaturated fatty acids.
authors.affiliation: Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232 Department of Chemistry, Tallinn University of Technology, 12618 Tallinn, Estonia.
authors.forename: Tarvi
authors.initials: T
authors.lastname: Teder
authors.affiliation: Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232.
authors.forename: William E
authors.initials: WE
authors.lastname: Boeglin
authors.affiliation: Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Brash
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000235:genetics / Q000378:metabolism*; D001093:Arachidonate 15-Lipoxygenase / Q000235:genetics / Q000378:metabolism*; D055162:Biocatalysis; D001792:Blood Platelets / Q000201:enzymology; D002851:Chromatography, High Pressure Liquid; D015777:Eicosanoids / Q000737:chemistry / Q000378:metabolism*; D004852:Epoxy Compounds / Q000737:chemistry / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006900:Hydroxylation; D008042:Linolenic Acids / Q000737:chemistry / Q000378:metabolism*; D008054:Lipid Peroxides / Q000737:chemistry / Q000378:metabolism*; D008084:Lipoxygenase / Q000378:metabolism*; D051379:Mice; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D011994:Recombinant Proteins / Q000378:metabolism; D030262:Soybean Proteins / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism
chemical_list: D015777:Eicosanoids; D004852:Epoxy Compounds; D008042:Linolenic Acids; D008054:Lipid Peroxides; D011994:Recombinant Proteins; D030262:Soybean Proteins; C046782:14,15-epoxy-5,8,11-eicosatrienoic acid; C101084:lipoxygenase L-1; D008084:Lipoxygenase; D001092:Arachidonate 12-Lipoxygenase; C515716:ALOX15 protein, human; D001093:Arachidonate 15-Lipoxygenase; D015126:8,11,14-Eicosatrienoic Acid
keywords: cytochrome P450; epoxyeicosatrienoic acid; fatty acid epoxide; fatty acid/physical chemistry; lipids/chemistry; lipoxygenase; monocyclic peroxide; nuclear magnetic resonance