Peroxynitrite-Mediated Decarboxylation of Pyruvate to Both Carbon Dioxide and Carbon Dioxide Radical Anion
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- 作者：Jeannette Vá ; squez-Vivar ; Ana Denicola ; Rafael Radi ; and Ohara Augusto
- 刊名：Chemical Research in Toxicology
- 出版年：1997
- 出版时间：July 1997
- 年：1997
- 卷：10
- 期：7
- 页码：786 - 794
- 全文大小：300K
- 年卷期：v.10,no.7(July 1997)
- ISSN：1520-5010
文摘
There has been a recent renewal of interest in the antioxidantproperties of pyruvate whichare usually attributed to its capacity to undergo oxidativedecarboxylation in the presence ofhydrogen peroxide. The interaction of pyruvate with otheroxidizing biological intermediates,however, has been scarcely considered in the literature. Here wereport that peroxynitrite,the oxidant produced by the reaction between superoxide anion andnitric oxide, reacts withpyruvate with an apparent second-order rate constant of 88 ± 7M-1 s-1 at pH 7.4and 37 
C.Kinetic studies indicated that pyruvate reacts with peroxynitriteanion (k = 100 ± 7 M-1s-1),peroxynitrous acid (k = 49 ± 7M-1 s-1), and ahighly oxidizing species derived from peroxynitrous acid. Pyruvate decarboxylation was proved by anion exchangechromatography detection of acetate in incubations of peroxynitrite and pyruvate at pH 7.4and 5.5. Formation ofcarbon dioxide radical anion was ascertained by EPR spin-trappingstudies in the presence ofGSH and the spin-trap 5,5-dimethyl-1-pyrroline N-oxide(DMPO). The use of pyruvate labeledwith 13C at the 1-position led to the detection of thelabeled DMPO carbon dioxide radicalanion adduct. In the absence of GSH, oxygen consumption studiesconfirmed that peroxynitritemediates the decarboxylation of pyruvate to free radical intermediates.Comparing the yieldsof acetate and free radicals estimated from the oxygen uptake studies,it is concluded thatpyruvate is oxidized by both one- and two-electron oxidation pathways,the latter beingpreponderant. Hydrogen peroxide-mediated pyruvate oxidation doesnot produce detectablelevels of carbon dioxide radical anion except in the presence ofiron(II)-ethylenediamine-N,N,N',N'-tetraacetate(EDTA). The apparent second-order rate constant of thereactionbetween pyruvate and hydrogen peroxide was determined to be 1 order ofmagnitude lowerthan that of the reaction between pyruvate and peroxynitrite. Thelatter process may contributeto the antioxidant properties of pyruvate.
C.Kinetic studies indicated that pyruvate reacts with peroxynitriteanion (k = 100 ± 7 M-1s-1),peroxynitrous acid (k = 49 ± 7M-1 s-1), and ahighly oxidizing species derived from peroxynitrous acid. Pyruvate decarboxylation was proved by anion exchangechromatography detection of acetate in incubations of peroxynitrite and pyruvate at pH 7.4and 5.5. Formation ofcarbon dioxide radical anion was ascertained by EPR spin-trappingstudies in the presence ofGSH and the spin-trap 5,5-dimethyl-1-pyrroline N-oxide(DMPO). The use of pyruvate labeledwith 13C at the 1-position led to the detection of thelabeled DMPO carbon dioxide radicalanion adduct. In the absence of GSH, oxygen consumption studiesconfirmed that peroxynitritemediates the decarboxylation of pyruvate to free radical intermediates.Comparing the yieldsof acetate and free radicals estimated from the oxygen uptake studies,it is concluded thatpyruvate is oxidized by both one- and two-electron oxidation pathways,the latter beingpreponderant. Hydrogen peroxide-mediated pyruvate oxidation doesnot produce detectablelevels of carbon dioxide radical anion except in the presence ofiron(II)-ethylenediamine-N,N,N',N'-tetraacetate(EDTA). The apparent second-order rate constant of thereactionbetween pyruvate and hydrogen peroxide was determined to be 1 order ofmagnitude lowerthan that of the reaction between pyruvate and peroxynitrite. Thelatter process may contributeto the antioxidant properties of pyruvate.