A comparative study of a cationic peroxidase from peanut and an anionic peroxidase from petunia

Summary

A comparative study on a pure cationic and a pure anionic protein from peanut cells and petunia stem tissue respectively, both with peroxidative activity, was made. The cationic protein weighs 44 Kd and the anionic 36 Kd. No immunological cross reactivity could be detected between the two proteins. In assays for peroxidative activity using the substrates 4-aminoantipyrine, guaiacol and eugenol it was noted that the anionic protein had 1.9, 12.7, and 27.7 fold greater enzymatic activity, respectively. For overall peroxidative measurements it is suggested that aminoantipyrine is probably the superior substrate. With regard to IAA oxidase activity of the two protein fractions it was noted that the cationic enzyme possessed optimal activity at pH 3.6 and the anionic protein at pH 7.0. The latter value could only be obtained by the addition of H₂O₂ and dichlorophenol (DCP). Since no additives were needed for the assay of IAA oxidation by the cationic protein it is suggested that this is a true IAA oxidase while the anionic fraction is a peroxidase involved in other reactions such as lignin biosynthesis.