title: Oxidation of indole-3-acetic acid by peroxidase: involvement of reduced peroxidase and compound III with superoxide as a product.
abstract: Kinetic and spectral data establish that peroxidase may oxidize indole-3-acetic acid by either of two pathways depending on the enzyme/substrate ratio. When relatively low enzyme/substrate ratios are employed, the oxidation proceeds through a reduced peroxidase in equilibrium compound III shuttle. Conversely, peroxidase operates through the conventionally accepted pathway involving native enzyme and compounds I and II only when high enzyme/substrate ratios are used. Compound III, a specific oxidase, constitutes the dominant steady-state form of peroxidase when the reduced peroxidase in equilibrium compound III shuttle is operational. Activation of this shuttle also produces a flux of superoxide anion radical at the expense of molecular oxygen. Thus, important biological consequences may follow activation of this shuttle under physiological conditions.
mesh_terms: D002374:Catalase / Q000494:pharmacology; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000378:metabolism*; D007700:Kinetics; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D013053:Spectrophotometry; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*
chemical_list: D007210:Indoleacetic Acids; D013481:Superoxides; C030737:indoleacetic acid; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; D010544:Peroxidases; D002374:Catalase; D013482:Superoxide Dismutase; D010100:Oxygen