The chemical nature of the second hydrogen peroxide compound formed by cytochrome c peroxidase and horseradish peroxidase. 1. Titration with reducing agents

Publisher Website
Google Scholar
Abstract
Spectrophotometric titrations of compound II formed by interaction of peroxidase and H2O2 with reducing agents such as ferrocyanide, ferrocytochrome c and ferrous ions, show it to undergo a 1-equivalent reduction to ferriperoxidase, the initial oxidation state of the enzyme. H2O2 or the anion O2H cannot, therefore, be a component part of its structure and it should no longer be regarded as an enzyme-substrate complex,Per.OOH, but as a compound in which the Fe has an effective oxidation number of +4. These results strongly support the following new mechanism for the interrelationship of compound I and compound II which necessitates a complete revision of the accepted mechanism for peroxidase action.[image] Preliminary values of 1.3-1.6 and approx. 1.0 V. have been estimated for the oxidation-reduction potentials of the compound l/compound II and compound II/peroxidase couples respectively at pH 5.3 (European convention). Four types of possible chemical structure for compound II containing Fe with an effective oxidation number of +4 are discussed, together with 2 general structures available for compound I, either as a ferric complex or a derivative containing Fe with an effective oxidation number of +5.