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Related Experiment Videos

Molecular oxygen modulates cytochrome c oxidase function

N S Chandel1, G R Budinger, P T Schumacker

  • 1Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.

The Journal of Biological Chemistry
|August 2, 1996
PubMed
Summary
This summary is machine-generated.

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Molecular oxygen reversibly inhibits cytochrome c oxidase, a key respiratory enzyme. This finding explains why low oxygen levels suppress cellular respiration, revealing a direct O2 interaction with the enzyme.

Area of Science:

  • Biochemistry
  • Mitochondrial respiration
  • Enzyme kinetics

Background:

  • Mitochondria exhibit suppressed State 3 respiration under low oxygen.
  • The underlying mechanism for this observation is not fully understood.
  • Cytochrome c oxidase is a critical enzyme in the electron transport chain.

Purpose of the Study:

  • To investigate the interaction between molecular oxygen and cytochrome c oxidase.
  • To determine if oxygen directly modifies the enzyme's catalytic activity.
  • To elucidate the mechanism behind oxygen-induced inhibition of respiration.

Main Methods:

  • Incubation of oxidized bovine heart cytochrome c oxidase at low oxygen concentrations (<50 microM).
  • Enzyme kinetic assays to measure Vmax and Km for cytochrome c and oxygen.

Related Experiment Videos

  • Spectroscopic analysis to assess the redox state of heme a3.

    • Main Results:

    • Low oxygen incubation caused a reversible decrease in Vmax and a slight increase in Km for cytochrome c oxidase.
    • Spectroscopy indicated increased reduction of heme a3 at lower oxygen levels, pinpointing the inhibition site.
    • The enzyme's optical absorption spectra remained unaffected, suggesting no structural changes.

    Conclusions:

    • Molecular oxygen directly interacts with cytochrome c oxidase, inhibiting its catalytic activity.
    • This interaction provides a mechanistic explanation for suppressed mitochondrial respiration at low oxygen.
    • The inhibition may occur via an allosteric effect of oxygen at the electron transfer site (heme a3 to O2).