The kinetics of the reaction of aquo Fe(III) myoglobin with hydrogen peroxide at pH 8

G. Marius Clore, Andrew N. Lane, Michael R. Hollaway

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6 Scopus citations

Abstract

The kinetics of the reaction of aquo Fe(III) myoglobin (Mb(III)) with H2O2 at pH 8.0 and 20° have been investigated quantitatively under non-linear second order conditions. The data obtained at five concentrations of H2O2 (molar ratio [H2O2]/[Mb]total in the range 0.3 to 4) were analysed simultaneously by means of non-linear numerical integration and optimization techniques. The only mechanism that satisfied the triple requirement of a standard deviation within the standard error of the experimental data, good determination of the optimized parameters and a random distribution of residuals is as follows: Mb(III) reacts with H2O2 to form species X with a second order rate constant k+1 = 3.53 × 102 M-1 s-1; species X in turn reacts with H2O2 to form species R with a second order rate constant k+2 = 3.40 × 103 M-1s-1; species R is then converted back into Mb(III) with a first order rate constant k=3 = 9.60 × 10-5 s-1. At 408 nm Δε{lunate}Mb(III)-R = 71.9 mM-1 cm-1 and δε{lunate}Mb(III)-X = 104 mM-1 cm-1. Species R is spectrally identical to the Fe(IV) myoglobin species described by George and Irvine [Biochem. J., 52, 511-517 (1952)]. The chemical nature of species X and R is discussed on the basis of the data in the present paper and data in the literature from EPR, Mössbauer, resonance Raman and magnetic susceptibility studies.

Original languageEnglish
Pages (from-to)139-146
Number of pages8
JournalInorganica Chimica Acta
Volume46
Issue numberC
DOIs
StatePublished - 1980

Bibliographical note

Funding Information:
We wish to thank the Science ResearchC ouncil for financial support. A.N.L. acknowledgest he receipt of an S.R.C. studentship.

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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