Purification and Characterization of Peroxidase Isoenzymes from Green Peas (Pisum sativum)

Abstract

ABSTRACT Peroxidase isoenzymes were purified from green peas with ion‐exchange chromatography on DEAE‐ and S‐Sepharose. Three isoenzymes were identified, one neutral (N) and two cationic (C1, C2). N was extremely heat labile, with 50% original activity lost after heating 1.5 min at 25°C. N had Km values (pH 5.0) of 10.2 mM and 2.6 mM for guaiacol and H 2 O 2 , respectively. C1 and C2 retained activity on heating at 30–70°C. C1 was able to reactivate after thermal inactivation. Km values for guaiacol/H 2 O 2 were 10.8 mM/7.2 mM (pH 5.0) and 10.8 mM/4.3 mM (pH 6.0) for C1 and C2, respectively. The three isoenzymes exhibited different peroxidase activities with different H‐donors, different sensitivities to cyanide and different abilities to catalyze oxidation of indoleacetic acid.