Kinetic evidence of horseradish peroxidase oxidation by compound I.
The kinetics of compound II formation, obtained upon mixing a highly purified horseradish peroxidase and hydrogen peroxide, was spectrophotometrically studied at three wavelengths in the absence of an added reducing agent. Our experiments confirm George's finding that more than one mole of compound II is formed per mole of hydrogen peroxide added. The new mechanism that we propose, contrary to the mechanism of George, is only valid when compound II is obtained in the absence of an added donor. Moreover, it is not inconsistent with the classical Chance mechanism of oxidation of an added donor by the system peroxidase -- hydrogen peroxide. According to this new mechanism, in the absence of an added donor, compound II formation involved two pathways. The first pathway is the monomolecular reduction of compound I by the endogenous donor, and the second pathway is the formation of two moles of compound II through the oxidoreduction reaction between one mole of peroxidase and one mole of compound I.
D006861:Hydrogen Peroxide / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D010944:Plants / Q000201:enzymology
D007527:Isoenzymes; D006861:Hydrogen Peroxide; D010544:Peroxidases