Molecular oxygen modulates cytochrome c oxidase function

Navdeep S. Chandel, G. R Scott Budinger, Paul T. Schumacker*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

124 Scopus citations


This study sought to determine whether molecular oxygen interacts with cytochrome c oxidase to modify its catalytic activity. Such an interaction could explain the observation that mitochondria incubated under low O2 concentrations exhibit a reversible suppression of State 3 respiration. Oxidized bovine heart cytochrome c oxidase was incubated in oxygen concentrations of <50 μM for 4 h. The enzyme exhibited a reversible decrease in V (max) after incubation, compared with control enzyme incubated at higher oxygen concentrations. This change was accompanied by a small increase in the apparent K(m) of the enzyme for both cytochrome c and oxygen, although the optical absorption spectra of oxidized, cycling, or reduced enzyme were not affected. Spectroscopy studies after 4 h of incubation revealed that heme a3 was 33% reduced during cycling at [O2] = 25 μM whereas enzyme at [O2] = 135 μM was only 18% reduced, suggesting that the site of inhibition occurred at the electron transfer step between heme a3 and O2. These results provide a mechanistic explanation for the observation that intact cells or mitochondria exhibit a reversible inhibition of respiration during prolonged exposure to [O2] <25 mM, by demonstrating that the catalytic activity of cytochrome c oxidase function is similarly inhibited, possibly through an allosteric effect of molecular O2 on the enzyme.

Original languageEnglish (US)
Pages (from-to)18672-18677
Number of pages6
JournalJournal of Biological Chemistry
Issue number31
StatePublished - 1996

ASJC Scopus subject areas

  • Molecular Biology
  • Biochemistry
  • Cell Biology


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