Journal article Open Access

Electron Leakage from the Mitochondrial NADPH-Adrenodoxin Reductase-Adrenodoxin-P450scc (Cholesterol Side Chain Cleavage) System

Hanukoglu, I.; Rapoport, R.; Weiner, L.; Sklan, D.

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  <identifier identifierType="URL"></identifier>
      <creatorName>Hanukoglu, I.</creatorName>
      <nameIdentifier nameIdentifierScheme="ORCID" schemeURI="">0000-0003-3889-0320</nameIdentifier>
      <creatorName>Rapoport, R.</creatorName>
      <creatorName>Weiner, L.</creatorName>
      <creatorName>Sklan, D.</creatorName>
    <title>Electron Leakage from the Mitochondrial NADPH-Adrenodoxin Reductase-Adrenodoxin-P450scc (Cholesterol Side Chain Cleavage) System</title>
    <date dateType="Issued">1993-09-01</date>
  <resourceType resourceTypeGeneral="Text">Journal article</resourceType>
    <alternateIdentifier alternateIdentifierType="url"></alternateIdentifier>
    <relatedIdentifier relatedIdentifierType="DOI" relationType="IsIdenticalTo">10.1006/abbi.1993.1452</relatedIdentifier>
    <rights rightsURI="info:eu-repo/semantics/openAccess">Open Access</rights>
    <description descriptionType="Abstract">In electron (e-) transfer systems some e- may "leak" reducing O2 to superoxide radical. This study examined the sites and kinetics of e- leakage from the mitochondrial P450scc system. Adrenodoxin reductase alone oxidized NADPH reducing O2 to superoxide radical at a very low rate. However, the reductase-adrenodoxin system reduced O2 at a rapid steady-state rate with Michaelis-Menten dependence on [adrenodoxin] (Vmax = 3.5 M e-/ min). After depletion of NADPH, reduced adrenodoxin was oxidized (auto-oxidation) with pseudo first order kinetics and the rate of e- transfer decreased ten fold. Ca2+ (&amp;lt; 1 mM) stimulated e- leakage in both phases. The reductase-adrenodoxin-P450scc system exhibited the highest rate of leakage (Vmax = 7.8 M e- / min). At low [adrenodoxin] the majority of e- leaked through P450scc and not through adrenodoxin. In the presence of the substrate, cholesterol, leakage drastically decreased to &amp;lt;0.5 M e- / min. These results indicate that the mitochondrial P450 systems can leak e-, producing O2 derived free radicals. Reduction of leakage during P450scc conversion of cholesterol to pregnenolone provides a clue to understanding physiological mechanisms that control e- leakage. These may include co-regulation of NADPH and cholesterol availability to the P450scc system, and a system of antioxidants for quenching the oxygen radicals.</description>
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