Indoleacetate oxidase activity of horseradish and other plant peroxidase isozymes

Zymographic analyses were carried out on a commercial peroxidasepreparation of horseradish (Cochlearia armorada) and crude extractsfrom several plant materials, such as roots of turnip, radish,spinach, sweet potato and morning glory, regarding the dualcatalytic activities of peroxidase- IA oxidase isozymes. A standardreacting mixture for the oxidase stain contained IA, TCP andFast Blue BB salt as substrate, promoting agent and dye coupler,respectively. An unidentified intermediate (or intermediates)resulting from enzymatic IA degradation was demonstrated tobe coupled with the diazonium salt and to form an insolublecomplex. At least four cathodal and four anodal peroxidase bandswere located in the horseradish preparation, the former appearingas dark IA oxidase bands and the latter as very faint bands. In the extracts from plant materials, less than half of thetotal peroxidase bands appeared as heavy to faint IA oxidasebands, whereas the remaining ones did not appear in the samecondition as that for the horseradish IA oxidase stain. Furthermore,it was noted that the intensity of each of the peroxidase bandswas not always correlated with that of the corresponding oxidasebands. ¹Contribution No. 683 from the National Institute of Genetics,Misima.