Kinetic characterisation and thermal inactivation study of partially purified red pepper (Capsicum annuum L.) peroxidase

Peroxidase (POD) from red sweet pepper cultured under an integrated system was partially purified, using a combination of phase partitioning with Triton X-114 and ammonium sulphate fractionation between 30 and 80%. The enzyme presented a single band in PAGE only when 4-MN was used as substrate. Optimum activity using ABTS as the H-donor was obtained at pH 4.5 and the apparent kinetic parameters Vm and KM were calculated for both ABTS and H2O2, showing a KM value in the same order in both cases (0.495 and 1.32 mM, respectively). The effect of several reducing agents was studied, ascorbic acid being the most active. The study of thermal inactivation showed a first-order inactivation kinetic, and the Arrhenius plot yielded a straight line with a slope equivalent to an activation energy of 151 kJ/mol. Significant inactivation occurred at temperature >40 °C and the D value for 5 min was 44.5 °C.