Document Detail


Rapid scavenging of peroxynitrous acid by monohydroascorbate.
MedLine Citation:
PMID:  14680676     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The reaction of peroxynitrous acid with monohydroascorbate, over the concentration range of 250 microM to 50 mM of monohydroascorbate at pH 5.8 and at 25 degrees C, was reinvestigated and the rate constant of the reaction found to be much higher than reported earlier (Bartlett, D.; Church, D. F.; Bounds, P. L.; Koppenol, W. H. The kinetics of oxidation of L-ascorbic acid by peroxynitrite. Free Radic. Biol. Med. 18:85-92; 1995; Squadrito, G. L.; Jin, X.; Pryor, W. A. Stopped-flow kinetics of the reaction of ascorbic acid with peroxynitrite. Arch. Biochem. Biophys. 322:53-59; 1995). The new rate constants at pH 5.8 are k1 = 1 x 10(6) M(-1) s(-1) and k(-1) = 500 s(-1) for 25 degrees C and k1 = 1.5 x 10(6) M(-1) s(-1) and k(-1) = 1 x 10(3) s(-1) for 37 degrees C. These values indicate that even at low monohydroascorbate concentrations most of peroxynitrous acid forms an adduct with this antioxidant. The mechanism of the reaction involves formation of an intermediate, which decays to a second intermediate with an absorption maximum at 345 nm. At low monohydroascorbate concentrations, the second intermediate decays to nitrate and monohydroascorbate, while at monohydroascorbate concentrations greater than 4 mM, this second intermediate reacts with a second monohydroascorbate to form nitrite, dehydroascorbate, and monohydroascorbate. EPR experiments indicate that the yield of the ascorbyl radical is 0.24% relative to the initial peroxynitrous acid concentration, and that this small amount of ascorbyl radicals is formed concomitantly with the decrease of the absorption at 345 nm. Thus, the ascorbyl radical is not a primary reaction product. Under the conditions of these experiments, no homolysis of peroxynitrous acid to nitrogen dioxide and hydroxyl radical was observed. Aside from monohydroascorbate's ability to "repair" oxidatively modified biomolecules, it may play a role as scavenger of peroxynitrous acid.
Authors:
Christophe R Kurz; Reinhard Kissner; Thomas Nauser; Daniel Perrin; Willem H Koppenol
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Free radical biology & medicine     Volume:  35     ISSN:  0891-5849     ISO Abbreviation:  Free Radic. Biol. Med.     Publication Date:  2003 Dec 
Date Detail:
Created Date:  2003-12-18     Completed Date:  2004-08-09     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8709159     Medline TA:  Free Radic Biol Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1529-37     Citation Subset:  IM    
Affiliation:
Laboratorium für Anorganische Chemie, Eidgenössische Technische Hochschule Zürich (Hönggerberg), Zürich, Switzerland.
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MeSH Terms
Descriptor/Qualifier:
Ascorbic Acid / chemistry*
Electron Spin Resonance Spectroscopy
Hydrogen-Ion Concentration
Kinetics
Peroxynitrous Acid / chemistry*
Chemical
Reg. No./Substance:
14691-52-2/Peroxynitrous Acid; 50-81-7/Ascorbic Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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