Abstract
The oxidation of indolylpropionic acid and indolylbutyric acid by O2 is catalyzed by. highly purified horseradish peroxidase preparations in the presence of Mn2+. The mechanism of the reaction has not been elucidated, but the formation of hydrogen peroxidase as an obligatory intermediate is suggested by the inhibiting effect of catalase. It is suggested that the previously reported oxidation of indolylpropionic acid and indolylbutyric acid by plant extracts may have been due to the presence of peroxidase and Mn2+ in the extracts.