Kinetics of the oxidation of reduced Cu,Zn-superoxide dismutase by peroxymonocarbonate

Kalina Ranguelova, Douglas Ganini, Marcelo G. Bonini, Robert E. London, Ronald P. Mason*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Kinetic evidence is reported for the role of the peroxymonocarbonate, HOOCO2-, as an oxidant for reduced Cu,Zn-superoxide dismutase-Cu(I) (SOD1) during the peroxidase activity of the enzyme. The formation of this reactive oxygen species results from the equilibrium between hydrogen peroxide and bicarbonate. Recently, peroxymonocarbonate has been proposed to be a key substrate for reduced SOD1 and has been shown to oxidize SOD1-Cu(I) to SOD1-Cu(II) much faster than H2O2. We have reinvestigated the kinetics of the reaction between SOD1-Cu(I) and HOOCO 2- by using conventional stopped-flow spectrophotometry and obtained a second-order rate constant of k=1600±100 M-1 s-1 for SOD1-Cu(I) oxidation by HOOCO2-. Our results demonstrate that peroxymonocarbonate oxidizes SOD1-Cu(I) to SOD1-Cu(II) and is in turn reduced to the carbonate anion radical. It is proposed that the dissociation of His61 from the active site Cu(I) in SOD-Cu(I) contributes to this chemistry by facilitating the binding of larger anions, such as peroxymonocarbonate.

Original languageEnglish (US)
Pages (from-to)589-594
Number of pages6
JournalFree Radical Biology and Medicine
Volume53
Issue number3
DOIs
StatePublished - Aug 1 2012
Externally publishedYes

Keywords

  • Carbonate anion radical
  • Peroxymonocarbonate
  • Superoxide dismutase

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)

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