The aerobic reactions of nitric oxide with cytochrome c were analysed. Nitric oxide (NO) reacts with ferrocytochrome c at a rate of 200 M-1 s-1 to form ferricytochrome cand nitroxyl anion (NO-). Ferricytochrome c was detected by optical spectroscopy; NO- was detected by trapping with metmyoglobin (Mb3+) to form the EPR-detectable Mb–nitrosyl complex, and by the formation of dimers in yeast ferrocytochrome cvia cross-linking of the free cysteine residue. The NO- formed subsequently reacted with oxygen to form peroxynitrite, as measured by the oxidation of dihydrorhodamine 123. NO binds to ferricytochrome c to form the ferricytochrome c-NO complex. The on-rate for this reaction is 1.3±0.4×103 M-1·s-1, and the off-rate is 0.087±0.054 s-1. The dissociation constant (Kd)of the complex is 22±7 µM. These reactions of NO with cytochrome c are likely to be relevant to mitochondrial metabolism of NO. Ferricytochrome c can act as a reversible sink for excess NO in the mitochondria. The reduction of NO to NO- by ferrocytochrome cmay play a role in the irreversible inhibition of mitochondrial oxygen consumption by peroxynitrite. It is generally assumed that peroxynitrite would be formed in mitochondria via the reaction of NO with superoxide. The finding that NO- is formed from the reaction of NO and ferrocytochrome c provides a means of producing peroxynitrite in the absence of superoxide, via the reaction of NO- with oxygen.
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Research Article|
May 15 1998
Reactions of nitric oxide with mitochondrial cytochrome c: a novel mechanism for the formation of nitroxyl anion and peroxynitrite Available to Purchase
Martyn A. SHARPE;
Martyn A. SHARPE
1Department of Biological Sciences, Central Campus, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, U.K.
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Chris E. COOPER
Chris E. COOPER
1
1Department of Biological Sciences, Central Campus, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, U.K.
1To whom correspondence should be addressed (e-mail [email protected]).
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Publisher: Portland Press Ltd
Received:
September 05 1997
Revision Received:
February 05 1998
Accepted:
March 02 1998
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1998
1998
Biochem J (1998) 332 (1): 9–19.
Article history
Received:
September 05 1997
Revision Received:
February 05 1998
Accepted:
March 02 1998
Citation
Martyn A. SHARPE, Chris E. COOPER; Reactions of nitric oxide with mitochondrial cytochrome c: a novel mechanism for the formation of nitroxyl anion and peroxynitrite. Biochem J 15 May 1998; 332 (1): 9–19. doi: https://doi.org/10.1042/bj3320009
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