Cited by 1,511Nitric Oxide and Endothelin EffectsRedox biology and oxidative stressFree Radicals and Antioxidants

The chemistry of peroxynitrite: A product from the reaction of nitric oxide with superoxide

Pryor, W. A., Squadrito, G. L.·1995·American Journal of Physiology-Lung Cellular and Molecular Physiology

Abstract

Nitric oxide and superoxide, which are produced by several cell types, rapidly combine to form peroxynitrite. This reaction can result in nitric oxide scavenging, and thus mitigation of the biological effects of superoxide. Also, superoxide can trap and hence modulate the effects of nitric oxide; superoxide dismutase, by controlling superoxide levels, therefore can influence the reaction pathways open to nitric oxide. The production of peroxynitrite, however, causes its own sequelae of events: Although neither .NO nor superoxide is a strong oxidant, peroxynitrite is a potent and versatile oxidant that can attack a wide range of biological targets. The peroxynitrite anion is relatively stable, but its acid, peroxynitrous acid (HOONO), rearranges to form nitrate with a half-life of approximately 1 s at pH 7, 37 degrees C. HOONO exists as a Boltzmann distribution of rotamers; at 5-37 degrees C HOONO has an apparent acidity constant, pKa,app, of 6.8. Oxidation reactions of HOONO can involve two-electron processes (such as an SN2 displacement) or a one-electron transfer (ET) reaction in which the substrate is oxidized by one electron and peroxynitrite is reduced. These oxidation reactions could involve one of two mechanisms. The first mechanism is homolysis of HOONO to give HO. and .NO2, which initially are held together in a solvent cage. This caged pair of radicals (the "geminate" pair) can either diffuse apart, giving free radicals that can perform oxidations, or react together either to form nitrate or to reform HOONO (a process called cage return). A large amount of cage return can explain the small entropy of activation (Arrhenius A-factor) observed for the decomposition of HOONO. A cage mechanism also can explain the residual yield of nitrate that appears to be formed even in the presence of high concentrations of all of the scavengers studied to date, since scavengers capture only free HO. and .NO2 and not caged radicals. If the cage mechanism is correct, the rate of disappearance of peroxynitrite be slower in solvents of higher viscosity, and we do not find this to be the case. The second mechanism is that an activated isomer of peroxynitrous acid, HOONO*, can be formed in a steady state. The HOONO* mechanism can explain the inability of hydroxyl radical scavengers to completely block either nitrate formation or the oxidation of substrates such as methionine, since HOONO* would be less reactive, and therefore more selective, than the hydroxyl radical itself.(ABSTRACT TRUNCATED AT 400 WORDS)

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Crossref · 10.1152/ajplung.1995.268.5.l699

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  • Peroxynitrite can nitrate tyrosine or tryptophan residues or oxidise methionine residues.

    “In addition, peroxynitrite is capable of nitrating tyrosine or tryptophan residues, or oxidising methionine residues [123,124,125,126,127,128].”

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Authors
Pryor, W. A., & Squadrito, G. L.
Affiliations
Louisiana State University (US)
Venue
American Journal of Physiology-Lung Cellular and Molecular Physiology
Published
1995-05-01
Volume
268
Issue
5
Pages
L699-L722
ISSN
  • 1040-0605 (ISSN-L)
  • 1522-1504
OpenAlex
W2209831038
Cited by
1,511
References
94
Citations by year
2026: 11 · 2025: 13 · 2024: 19 · 2023: 21 · 2022: 21 · 2021: 19 · 2020: 24 · 2019: 28 · 2018: 29 · 2017: 30 · 2016: 30 · 2015: 35 · 2014: 42 · 2013: 55 · 2012: 47
FWCI
52.08
Type
journal article
Language
en
Open access
closed
Locations
  • American Journal of Physiology-Lung Cellular and Molecular Physiology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Physiology › Nitric Oxide and Endothelin Effects
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Redox biology and oxidative stress
  • Physical Sciences › Chemistry › Organic Chemistry › Free Radicals and Antioxidants
Keywords
peroxynitrite, nitric oxide, superoxide, peroxynitrous acid, nitrate formation, superoxide dismutase, nitric oxide scavenging, single electron transfer, two-electron oxidation, peroxynitrite decomposition, hydroxyl radical scavengers, nitric oxide synthase, nitric oxide signaling
MeSH terms
Animals, Humans, Hydrogen-Ion Concentration, Hydroxylation, Methionine, Nitrates, Nitric Oxide, Nitroso Compounds, Oxidation-Reduction, Sulfhydryl Compounds, Superoxides, Viscosity

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