Cytokinin control in subcellular localization of indoleacetic acid oxidase and peroxidase

IAA oxidase and peroxidase were found in all subcellular fractions of tobacco callus cells. The bound and cytoplasmic fractions differed greatly in IAA oxidase/peroxidase ratio and in isoperoxidase composition. The IAA oxidase/peroxidase ratio was particularly high in the plasma membrane-rich fraction. Kinetin had profound effects on IAA oxidase and peroxidase. The appearance of fast migrating isoperoxidases in response to 0·2 μM kinetin was found only in cytoplasmic, plasma membrane and ribosome-rich fractions; a high concentration of kinetin inhibited their formation. High kinetin concentrations also lowered the specific activity of IAA oxidase and peroxidase in all subcellular fractions, but the effect was much greater on peroxidase than on IAA oxidase, thus resulting in a drastic increase in IAA oxidase/peroxidase ratio. Evidently the activities of IAA oxidase and peroxidase were not equivalent and should be considered separately.