Characterisation of an anionic peroxidase from horseradish cv. Balady

An anionic peroxidase POIII, molecular weight 56 kDa, was purified from the roots of horseradish cv. Balady. The enzyme exhibited high activity towards o-phenylenediamine and guaiacol, while o-dianisidine had moderate peroxidase activity. Pyrogallol and p-aminoantipyrine had low affinity toward POIII. POIII was found to have a temperature optimum at 40 °C; the enzyme activity remained stable up to 40 °C and retained 87%, 51% and 29% of its activity at 50, 60 and 70 °C, respectively. The enzyme exhibited more than 50% of activity in the pH range between 4.0 and 8.0 with its pH optimum at 5.5. Several metal cations had partial inhibitory effects toward POIII. Fe3+ enhanced the activity of the enzyme by 160% at 5 mM. All the metal chelators caused partial inhibitory effects toward POIII, except for EDTA at 1 mM, which had no effect on the enzyme.