The lipoxygenase gene ALOXE3 implicated in skin differentiation encodes a hydroperoxide isomerase.

Yu Z, Schneider C, Boeglin WE, Marnett LJ, Brash AR
Proc Natl Acad Sci U S A. 2003 100 (16): 9162-7

PMID: 12881489 · PMCID: PMC170889 · DOI:10.1073/pnas.1633612100

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.

MeSH Terms (21)

Catalysis Cell Differentiation Chromatography, High Pressure Liquid Circular Dichroism DNA, Complementary Dose-Response Relationship, Drug Gas Chromatography-Mass Spectrometry Humans Hydrogen Peroxide Intramolecular Oxidoreductases Keratinocytes Kinetics Lipoxygenase Magnetic Resonance Spectroscopy Masoprocol Mass Spectrometry Models, Chemical Mutation Oxidation-Reduction Signal Transduction Skin

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