The function of free carboxyl groups in the action of peroxidase and indole-3-acetic acid oxidase

The extracellular peroxidase from cultures of Inonotus radiatus and of peanut (Arachis hypogeaL.) cells as well as the mycelial peroxidase from Trametes versicolor were used for studies of immobilizing this protein either by its free amino or its carboxyl groups. The immobilization process was carried out either on keratin proteins derived from feathers or on polyamide coated over silica gel. Coupling was established either through the free amino or carboxyl groups. In general the indolyl-3-acetic acid oxidase activity of fungal peroxidases exceeds that of peanut peroxidase. When the peroxidase of the three sources was immobilized on the matrices by the free amino groups, little if any effect on the IAA oxidase activity could be measured. However, immobilization through the carboxyl groups resulted in a drastic reduction of indole-3-acetic acid oxidase activity. Since identical amounts of peroxidase were linked in all cases, the loss of indolyl-3-acetic acid oxidase activity implies that the carboxyl group is essential for the active site.