Albumin Oxidation to Diverse Radicals by the Peroxidase Activity of Cu,Zn-Superoxide Dismutase in the Presence of Bicarbonate or Nitrite: Diffusible Radicals Produce Cysteinyl and Solvent-Exposed and -Unexposed Tyrosyl Radical

Marcelo G. Bonini, Denise C. Fernandes, Ohara Augusto*

*Corresponding author for this work

Research output: Contribution to journalArticle

58 Scopus citations

Abstract

The peroxidase activity of Cu,Zn-superoxide dismutase (Cu,Zn-SOD) has been extensively studied in recent years due to its potential relationship to familial amyothrophic lateral sclerosis. The mechanism by which Cu,Zn-SOD/hydrogen peroxide/bicarbonate is able to oxidize substrates has been proposed to be dependent on an oxidant whose nature, diffusible carbonate radical anion or enzyme-bound peroxycarbonate, remains debatable. One possibility to distinguish these species is to examine whether protein targets are oxidized to protein radicals. Here, we used EPR methodologies to study bovine serum albumin (BSA) oxidation by Cu,Zn-SOD/hydrogen peroxide in the absence and presence of bicarbonate or nitrite. The results showed that BSA oxidation in the presence of bicarbonate or nitrite at pH 7.4 produced mainly solvent-exposed and -unexposed BSA-tyrosyl radicals, respectively. Production of the latter was shown to be preceded by BSA-cysteinyl radical formation. The results also showed that hydrogen peroxide/bicarbonate extensively oxidized BSA-cysteine to the corresponding sulfenic acid even in the absence of Cu,Zn-SOD. Thus, our studies support the idea that peroxycarbonate acts as a two-electron oxidant and may be an important biological mediator. Overall, the results prove the diffusible and radical nature of the oxidants produced during the peroxidase activity of Cu,Zn-SOD in the presence of bicarbonate or nitrite.

Original languageEnglish (US)
Pages (from-to)344-351
Number of pages8
JournalBiochemistry
Volume43
Issue number2
DOIs
StatePublished - Jan 20 2004
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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