Biosynthesis of 5-Oxo-6,8,11,14-eicosatetraenoic Acid from 5-Hydroperoxyeicosatetraenoic Acid in the Murine Macrophage*

  1. Robert C. Murphy
  1. From the Division of Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, Colorado 80206

Abstract

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a metabolite of arachidonic acid shown to possess important biological activities within different cell types. In the neutrophil, a specific NADP+-dependent dehydrogenase utilizes 5-lipoxygenase-derived 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5(S)-HETE) as the required substrate. In the present study, 5-hydroperoxy-6,8,11,14-eicosatetraenoic acid (5-HpETE), rather than 5-HETE, was found to be the biosynthetic precursor of 5-oxo-ETE in the murine macrophage. The macrophage was not able to convert 5-HETE into 5-oxo-ETE even when preincubated with phorbol ester or with other lipid hydroperoxides. The factor responsible for the conversion of 5-HpETE into 5-oxo-ETE was found predominantly in the cytosolic fraction of the macrophage, with an approximate molecular weight of 50,000–60,000, as assessed by size exclusion chromatography. Formation of 5-oxo-ETE was rapid and the catalytic protein was found to have an apparent K m of 5.3 μm for the eicosanoid. Furthermore, the protein could efficiently utilize 5(R,S)-HpETE as substrate and was heat and protease labile. This novel pathway of 5-oxo-ETE biosynthesis in the murine macrophage was consistent with reduction of a 5-hydroperoxy group to an intermediate alkoxy radical that could be subsequently oxidized to the 5-oxo product. Such a mechanism would enable racemic 5-HpETE, derived from free radical oxidation of arachidonic acid, to be efficiently converted into this potent chemotactic eicosanoid.

  • Abbreviations:
    5(S)-HpETE
    5-hydroperoxy-6,8,11,14-eicosatetraenoic acid
    5(S)-HETE
    5-hydroxy-6,8,11,14-eicosatetraenoic acid
    LTA4
    leukotriene A4
    5-oxo-ETE
    5-oxo-6,8,11,14-eicosatetraenoic acid
    PMA
    phorbol myristate acetate
    RP-HPLC
    reverse phase-high performance liquid chromatography
    • Received August 20, 2002.
    • Revision received January 22, 2003.
    Table of Contents

    This Article

    1. The Journal of Biological Chemistry 278, 11190-11196.
    1. All Versions of this Article:
      1. M208496200v1
      2. 278/13/11190 (most recent)

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