Effect of indoleacetic Acid and hydroxyproline on isoenzymes of peroxidase in wheat coleoptiles

Indoleacetic acid at 0.017 millimolar inhibited the formation of three peroxidase isoenzymes in both soluble and wall-bound enzyme fractions of wheat coleoptile (Triticum vulgare) tissue. Hydroxyproline at 1 millimolar prevented the indoleacetic acid-induced inhibition. Indoleacetic acid oxidase activity in the soluble fraction was decreased by indoleacetic acid and was restored by hydroxyproline. Most of the indoleacetic acid oxidase activity was located in the electrophoretic zones occupied by two of the peroxidase isoenzymes influenced by indoleacetic acid and hydroxyproline. At least part of the effect of hydroxyproline on auxin-induced elongation of coleoptile tissue may be through control of auxin levels by indoleacetic acid oxidase.