Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1994 Nov 8;91(23):11173-7.
doi: 10.1073/pnas.91.23.11173.

One- and two-electron oxidations of methionine by peroxynitrite

W A Pryor  1 , X Jin, G L Squadrito
Affiliations

One- and two-electron oxidations of methionine by peroxynitrite

W A Pryor et al. Proc Natl Acad Sci U S A. .

Abstract

Peroxynitrite is stable, but its acid, HOONO, either rearranges to form nitrate or oxidizes nearby biomolecules. We report here the reactions of HOONO with methionine and the methionine analog 2-keto-4-thiomethylbutanoic acid (KTBA). These oxidations proceed by two competing mechanisms. The first yields the sulfoxide; the second-order rate constants, k2, for this process for methionine and KTBA are 181 +/- 8 and 277 +/- 11 M-1.s-1, respectively, at pH 7.4 and 25 degrees C. In the second mechanism, methionine or KTBA undergoes a one-electron oxidation that ultimately gives ethylene. We propose that the one-electron oxidant is an activated form of peroxynitrous acid, HOONO*, that is formed in a steady state mechanism. The ratios of the second-order rate constants for the ethylene-producing reaction (k*2) and the first-order rate constant to produce nitric acid (kN) for methionine and KTBA, k*2/kN, are 1250 +/- 290 and 6230 +/- 1390 M-1, respectively. Both ceric and peroxydisulfate ions also oxidize KTBA to ethylene, confirming a one-electron transfer mechanism. The yields of neither MetSO nor ethylene are affected by several hydroxyl radical scavengers, suggesting that a unimolecular homolysis of HOONO to HO. and .NO2 is not involved in these reactions. HOONO* gives hydroxyl radical-like products from various substrates but displays more selectivity than does the hydroxyl radical; thus, HOONO* is incompletely trapped by typical HO. scavengers. However, a mechanism involving dissociation of HOONO* to caged radicals cannot be ruled out at this time.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. J Biol Chem. 1970 Sep 25;245(18):4641-6 - PubMed
    1. Free Radic Biol Med. 1994 Aug;17(2):127-60 - PubMed
    1. Life Sci. 1980 Sep 1;27(9):731-8 - PubMed
    1. Arch Biochem Biophys. 1983 May;223(1):271-81 - PubMed
    1. Nature. 1986 Apr 3-9;320(6061):454-6 - PubMed

Publication types

LinkOut - more resources

-