Hydrogen Peroxide-mediated Oxidation of Indole-3-acetic Acid by Tomato Peroxidase and Molecular Oxygen.

The oxidation of indole-3-acetic acid by anionic tomato peroxidase was found to be negligible unless reaction mixtures were supplemented with H(2)O(2). The addition of H(2)O(2) to reaction mixtures initiated a period of rapid indole-3-acetic acid oxidation and O(2) uptake; this phase ended and O(2) uptake fell to a low level when the H(2)O(2) was exhausted. The stoichiometry of the reaction, which is highly dependent on enzyme concentration and pH, suggests that H(2)O(2) initiates a sequence of reactions in which indole-3-acetic acid is oxidized.