Characterization and function of mitochondrial nitric-oxide synthase

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140 Scopus citations


The mitochondrial production of nitric oxide is catalyzed by a nitric-oxide synthase. This enzyme has the same cofactor and substrate requirements as other constitutive nitric-oxide synthases. Its occurrence was demonstrated in various mitochondrial preparations (intact, purified mitochondria, permeabilized mitochondria, mitoplasts, submitochondrial particles) from different organs (liver, heart) and species (rat, pig). Endogenous nitric oxide reversibly inhibits oxygen consumption and ATP synthesis by competitive inhibition of cytochrome oxidase. The increased Km of cytochrome oxidase for oxygen and the steady-state reduction of the electron chain carriers provided experimental evidence for the direct interaction of this oxidase with endogenous nitric oxide. The increase in hydrogen peroxide production by nitric oxide-producing mitochondria not accompanied by the full reduction of the respiratory chain components indicated that cytochrome c oxidase utilizes nitric oxide as an alternative substrate. Finally, effectors or modulators of cytochrome oxidase (the irreversible step in oxidative phosphorylation) had been proposed during the last 40 years. Nitric oxide is the first molecule that fulfills this role (it is a competitive inhibitor, produced at a fair rate near the target site) extending the oxygen gradient to tissues.

Original languageEnglish (US)
Pages (from-to)397-408
Number of pages12
JournalFree Radical Biology and Medicine
Issue number4
StatePublished - Feb 15 2003
Externally publishedYes


  • Free radicals
  • Mitochondria
  • Mitochondrial metabolism
  • Nitric oxide
  • Nitric-oxide synthase
  • Oxygen consumption

ASJC Scopus subject areas

  • Medicine(all)
  • Toxicology
  • Clinical Biochemistry


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