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Mechanism of superoxide and hydrogen peroxide generation by human electron-transfer flavoprotein and pathological variants.

Abstract

Reactive oxygen species production by mitochondrial enzymes plays a fundamental role both in cellular signaling and in the progression of dysfunctional states. However, sources of reactive oxygen species and the mechanisms by which enzymes produce these reactive species still remain elusive. We characterized the generation of reactive oxygen species by purified human electron-transfer flavoprotein (ETF), a mitochondrial enzyme that has a central role in the metabolism of lipids, amino acids, and choline. The results showed that ETF produces significant amounts of both superoxide and hydrogen peroxide in the presence of its partner enzyme medium-chain acyl-CoA dehydrogenase (MCAD). ETF-mediated production of reactive oxygen species is partially inhibited at high MCAD/ETF ratios, whereas it is enhanced at high ionic strength. Determination of the reduction potentials of ETF showed that thermodynamic properties of the FAD cofactor are changed upon formation of a complex between ETF and MCAD, supporting the notion that protein:protein interactions modulate the reactivity of the protein with dioxygen. Two pathogenic ETF variants were also studied to determine which factors modulate the reactivity toward molecular oxygen and promote reactive oxygen species production. The results obtained show that destabilized conformations and defective protein:protein interactions increase the ability of ETF to generate reactive oxygen species. A possible role for these processes in mitochondrial dysfunction in metabolic disorders of fatty acid β-oxidation is discussed.

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  • Publisher Full Text

    • Authors

    Rodrigues JV, Gomes CM

    Institution

    Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal.

    Source

    Free radical biology & medicine 53:1 2012 Jul 1 pg 12-9

    MeSH

    Acyl-CoA Dehydrogenase
    Electron Transport
    Electron-Transferring Flavoproteins
    Humans
    Hydrogen Peroxide
    Kinetics
    Models, Molecular
    Mutagenesis, Site-Directed
    Oxidation-Reduction
    Point Mutation
    Protein Binding
    Superoxides
    Thermodynamics

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    22588007