Properties of anionic peroxidases purified from Chinese cabbage roots

Two anionic peroxidases were isolated from Chinese cabbage roots and purified using gel filtration followed by ion-exchange chromatography. Following purification a specific activity of peroxidases was estimated as 50 units.mg-1 (A1) and 30 units.mg-1 (A2) compared with that of a crude extract of the peroxidases which was 2.31 units.mg-1. The pH for its optimum activity was 5.0 and the addition of Ca2+ produced a 15 % increase in peroxidase activity. Isoelectric focusing techniques were carried out in order to classify the peroxidases based on their isoelectric point (pI). Two anionic peroxidases, A1 and A2, were found to have pI values of 4.83 and 4.78, respectively. The peroxidases were found to be heat-stable, with 20 % (A1) and 16 % (A2) of the enzymatic activity remaining after heat treatment at 70 °C for 20 min. The heat inactivation rate followed first-order kinetics with the activation energy; Ea, estimated as 38.2 kcal.mol-1 and 36.4 kcal.mol-1 for A1 and A2, respectively.