PURIFICATION, CHARACTERIZATION AND CATALYTIC ACTIVITY OF ANIONIC ZUCCHINI PEROXIDASE

The isolation and purification, by preparative electrofocusing, of the major anionic (ZPOA) and cationic (ZPOC) isoenzymes, collected from y oung zucchini squash, are reported. The M(r) and sugar content are sim ilar to those found previously for the major isoenzymes from the ripe fruits and in the range commonly observed for plant peroxidases. The a mount of the two cationic enzymes was very low compared with that of a nionic ZPOA. The anionic enzyme has been characterized by electronic, circular dichroism, proton NMR and electron paramagnetic resonance spe ctroscopy. The spectra are qualitatively similar to those of the corre sponding anionic horseradish peroxidase (HRPA) derivatives, with minor differences attributable to the particular protein environment around the heme. The kinetics of the enzymatic oxidation of a series of phen ols by H2O2 have been studied. ZPOA shows a parallel behavior to HRPA, but it is systematically more active than HRPA, indicating that the z ucchini enzymes have a marked tendency to carry out oxidation of this type of compounds.