Oct 10, 1976

Stoichiometry of the reaction between horseradish peroxidase and p-cresol

The Journal of Biological Chemistry
W D Hewson, H B Dunford

Abstract

Over a wide range of pH horseradish peroxidase compound I can be reduced quantitatively via compound II to the native enzyme by only 1 molar equivalent of p-cresol. Since 2 molar equivalents of electrons are required for the single turnover of the enzymatic cycle, p-cresol behaves as a 2-electron reductant. With p-cresol and compound I in a 1:1 ratio compound II and p-methylphenoxy radicals are obtained in the transient state. Compound II is then reduced to the native enzyme. A possible explanation for the facile reduction of compound II involves reaction with the dimerization product of these radicals, 1/2 molar equivalent of 2,2'-dihydroxy-5,5'-dimethylbiphenyl. If only 1/2 molar equivalent of p-cresol is present, than at high pH the reduction stops at compound II. The major steady state peroxidase oxidation product of p-cresol (with p-cresol in large excess compared to the enzyme concentration) is Pummerer's ketone. Pummerer's ketone is only reactive at pH values greater than about 9 where significant amounts of the enol can be formed via the enolate anion. Therefore, in alkaline solution it is reactive with compound I, but not with compound II, which is converted into an unreactive basic form. These results indicate that Pu...Continue Reading

  • References
  • Citations

References

  • We're still populating references for this paper, please check back later.
  • References
  • Citations

Citations

  • This paper may not have been cited yet.

Mentioned in this Paper

Ovoperoxidase
Alpha-Peroxidase
Peroxidases
Free Radicals
Horseradish peroxidase compound I
Radicals (chemistry)
Plasma Protein Binding Capacity
Oxidation
Protein Conformation
Spectrophotometry, Ultraviolet

About this Paper

Related Feeds

ASBMB Publications

The American Society for Biochemistry and Molecular Biology (ASBMB) includes the Journal of Biological Chemistry, Molecular & Cellular Proteomics, and the Journal of Lipid Research. Discover the latest research from ASBMB here.

Related Papers

The Journal of Biological Chemistry
W D Hewson, H B Dunford
Archives of Biochemistry and Biophysics
A CelikE Lloyd Raven
Biochemical and Biophysical Research Communications
D Y Cai, M Tien
© 2020 Meta ULC. All rights reserved