The Role of Indole-3-Acetic Acid in Peroxidase Oxidation of Ascorbic Acid Catalyzed by Horseradish Peroxidase

摘要

We studied stationary kinetics of ascorbic acid oxidation in the presence of indole-3-acetic acid catalyzed by horseradish peroxidase. The catalytic (k_(cat) and K_m) and inhibition (K_i) constants were determined for pH from 4.5 to 7.0. The auxin proved to competitively inhibit the enzyme when a single ascorbic acid molecule is bound, while a non-competitive inhibition by IAA is observed for peroxidase oxidation of two or more substrate molecules. A mechanism of ascorbic acid oxidation in the presence of indole-3-acetic acid is proposed.