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Simultaneous Measurement of Superoxide/Hydrogen Peroxide and NADH Production by Flavin-containing Mitochondrial Dehydrogenases
08:57

Simultaneous Measurement of Superoxide/Hydrogen Peroxide and NADH Production by Flavin-containing Mitochondrial Dehydrogenases

Published on: February 24, 2018

Partitioning of superoxide and hydrogen peroxide production by mitochondrial respiratory complex I

Vera G Grivennikova1, Andrei D Vinogradov

  • 1Department of Biochemistry, Moscow State University, Moscow, Russian Federation.

Biochimica Et Biophysica Acta
|January 15, 2013
PubMed

Insights

Mitochondrial complex I generates both superoxide and hydrogen peroxide. Different sites, FMNH(-) and iron-sulfur center N-2, are responsible for hydrogen peroxide and superoxide production, respectively.

Area of Science:

  • Biochemistry
  • Mitochondrial Physiology
  • Oxidative Stress

Background:

  • Mitochondrial respiratory complex I plays a crucial role in cellular energy production.
  • Complex I is also implicated in the generation of reactive oxygen species (ROS), contributing to oxidative stress.
  • Understanding the mechanisms of ROS production by complex I is vital for comprehending cellular redox balance.

Purpose of the Study:

  • To investigate the specific sites and mechanisms of superoxide and hydrogen peroxide formation by membrane-bound respiratory complex I.
  • To characterize the kinetics of ROS production in relation to NADH concentration and redox state.
  • To elucidate the roles of different redox centers within complex I in ROS generation.

Main Methods:

  • Utilized inside-out submitochondrial particles (SMP) and purified complex I.
  • Performed NADH- and succinate-supported reactions to assess ROS production.
  • Analyzed kinetic dependencies of superoxide and hydrogen peroxide formation on NADH concentration and NAD(+)/NADH ratios.
  • Investigated the effects of guanidine on complex I activity and ROS generation.

Main Results:

  • Complex I catalyzes both superoxide and hydrogen peroxide formation, with a ratio of approximately 0.7 at optimal NADH.
  • Superoxide production decreases at high NADH concentrations, while hydrogen peroxide formation remains insensitive.
  • Hydrogen peroxide production fits a Nernst equation for a two-electron donor, suggesting FMNH(-), while superoxide production kinetics point to the N-2 iron-sulfur center.
  • Guanidine significantly stimulates ROS production and alters reductase activities.

Conclusions:

  • At least two distinct sites within complex I contribute to ROS generation: FMNH(-) for hydrogen peroxide and the N-2 iron-sulfur center for superoxide.
  • The differential regulation of superoxide and hydrogen peroxide production by NADH concentration highlights distinct physiological roles.
  • These findings provide a deeper mechanistic understanding of complex I-mediated oxidative stress.

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