title: Kinetic and mechanistic considerations to assess the biological fate of peroxynitrite.
abstract: BACKGROUND
  Peroxynitrite, the product of the reaction between superoxide radicals and nitric oxide, is an elusive oxidant with a short half-life and a low steady-state concentration in biological systems; it promotes nitroxidative damage.
  
  
  METHODS
  We will consider kinetic and mechanistic aspects that allow rationalizing the biological fate of peroxynitrite from data obtained by a combination of methods that include fast kinetic techniques, electron paramagnetic resonance and kinetic simulations. In addition, we provide a quantitative analysis of peroxynitrite production rates and conceivable steady-state levels in living systems.
  
  
  CONCLUSIONS
  The preferential reactions of peroxynitrite in vivo include those with carbon dioxide, thiols and metalloproteins; its homolysis represents only <1% of its fate. To note, carbon dioxide accounts for a significant fraction of peroxynitrite consumption leading to the formation of strong one-electron oxidants, carbonate radicals and nitrogen dioxide. On the other hand, peroxynitrite is rapidly reduced by peroxiredoxins, which represent efficient thiol-based peroxynitrite detoxification systems. Glutathione, present at mM concentration in cells and frequently considered a direct scavenger of peroxynitrite, does not react sufficiently fast with it in vivo; glutathione mainly inhibits peroxynitrite-dependent processes by reactions with secondary radicals. The detection of protein 3-nitrotyrosine, a molecular footprint, can demonstrate peroxynitrite formation in vivo. Basal peroxynitrite formation rates in cells can be estimated in the order of 0.1 to 0.5μMs(-1) and its steady-state concentration at ~1nM.
  
  
  CONCLUSIONS
  The analysis provides a handle to predict the preferential fate and steady-state levels of peroxynitrite in living systems. This is useful to understand pathophysiological aspects and pharmacological prospects connected to peroxynitrite. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.
authors.affiliation: Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
authors.forename: Sebastián
authors.initials: S
authors.lastname: Carballal
authors.forename: Silvina
authors.initials: S
authors.lastname: Bartesaghi
authors.forename: Rafael
authors.initials: R
authors.lastname: Radi
mesh_terms: D000818:Animals; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D006801:Humans; D007700:Kinetics; D030421:Peroxynitrous Acid / Q000032:analysis* / Q000378:metabolism*
chemical_list: D030421:Peroxynitrous Acid
keywords: 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid); 3-nitrotyrosine; 5,5-dimethyl-1-pyrroline-N-oxide; ABTS(2−); DMPO; DTPA; EPO; Free radical; GSH; MPO; NOS; NT; Nitric oxide; Nitrotyrosine; Oxidative stress; Peroxynitrite; Prx; SOD; Superoxide radical; diethylenetriaminepentaacetic acid; eosinophil peroxidase; glutathione; myeloperoxidase; nitric oxide synthase; peroxiredoxin; superoxide dismutase