title: The lipoxygenase gene ALOXE3 implicated in skin differentiation encodes a hydroperoxide isomerase.
abstract: Lipoxygenase (LOX) enzymes form fatty acid hydroperoxides used in membrane remodeling and cell signaling. Mammalian epidermal LOX type 3 (eLOX3) is distinctive in totally lacking this typical oxygenase activity. Surprisingly, genetic evidence has linked mutations in eLOX3 or a colocalizing enzyme, 12R-LOX, to disruption of the normal permeability barrier of the skin [Jobard, F., Lefèvre, C., Karaduman, A., Blanchet-Bardon, C., Emre, S., Weissenbach, J., Ozgüc, M., Lathrop, M., Prud'homme, J. F. & Fischer, J. (2002) Hum. Mol. Genet. 11, 107-113]. Herein we identify a logical link of the biochemistry to the genetics. eLOX3 functions as a hydroperoxide isomerase (epoxyalcohol synthase) by using the product of 12R-LOX as the preferred substrate. 12R-Hydroperoxyeicosatetraenoic acid (12R-HPETE) is converted to 8R-hydroxy-11R,12R-epoxyeicosa-5Z,9E,14Z-trienoic acid, one of the isomers of hepoxilin A3, and to 12-ketoeicosatetraenoic acid in a 2:1 ratio. Other hydroperoxides, including 8R-HPETE, 12S-HPETE, and 15S-HPETE, as well as the 13S- and 13R-hydroperoxides of linoleic acid are converted less efficiently. Mass spectrometric analysis of the epoxyalcohol formed from [18O]15S-HPETE showed that both hydroperoxy oxygens are retained in the product. We propose that the ferrous form of eLOX3 initiates a redox cycle, unprecedented among LOX in being autocatalytic, in which the hydroperoxy substrate is isomerized to the epoxyalcohol or keto product. Our results provide strong biochemical evidence for a functional linkage of 12R-LOX and eLOX3 and clues into skin biochemistry and the etiology of ichthyosiform diseases in humans.
authors.affiliation: Department of Pharmacology, Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
authors.forename: Zheyong
authors.initials: Z
authors.lastname: Yu
authors.forename: Claus
authors.initials: C
authors.lastname: Schneider
authors.forename: William E
authors.initials: WE
authors.lastname: Boeglin
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Marnett
authors.forename: Alan R
authors.initials: AR
authors.lastname: Brash
mesh_terms: D002384:Catalysis; D002454:Cell Differentiation; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D019746:Intramolecular Oxidoreductases / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology*; D015603:Keratinocytes / Q000378:metabolism; D007700:Kinetics; D008084:Lipoxygenase / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009637:Masoprocol / Q000737:chemistry; D013058:Mass Spectrometry; D008956:Models, Chemical; D009154:Mutation; D010084:Oxidation-Reduction; D015398:Signal Transduction; D012867:Skin / Q000166:cytology / Q000201:enzymology*
chemical_list: D018076:DNA, Complementary; D009637:Masoprocol; D006861:Hydrogen Peroxide; D008084:Lipoxygenase; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase