Oxidation of Indole-3-Acetylaspartic Acid in Vicia

Abstract

Oxidation of IAA catalyzed by peroxidase and IAA oxidase with accompanying decarboxylation has been extensively studied [17, 18, 20, 21] and enzymatic kinetics of horseradish peroxidase and reaction products of IAA have been elucidated [8, 9, 12, 14]. In some plant species, however, peroxidative decarboxylation of IAA was reported to be a minor component in Zea seedlings [6, 15] and in Pinus seeds [7], where IAA was oxidized to OxIAA [19]. In the present report, we show another IAA oxidation system without decarboxylation in Vicia seedlings, where IAA-Asp was oxidized to dioxindole-3-acetic acid (DIA) conjugates, and a possibility that peroxidase could contribute to the IAA-Asp oxidation was also examined.