Characterization of ionically bound peroxidases from apple (Mallus pumilus) fruits

Ionically bound peroxidases (POD) were salt extracted from the pulp of four Indian apple varieties, i.e., Golden delicious HP, Golden delicious JK, Red delicious, and Royal delicious. They were precipitated with chilled ethanol. Thermal treatments of partially purified enzymes were given from 40-70 degrees C for 30 minutes. Golden delicious HP peroxidase showed thermostability at 60 degrees C, while three other peroxidases were observed at 50 degrees C. Phenolic compounds (i.e., caffeic acid, ferulic acids, p-coumaric acid, protocatechuic acid) and metal ions (i.e., Cu2+ and Fe2+) activated all apple peroxidases. However, Mn2+ inhibited the peroxidases from Golden delicious HP, Golden delicious JK, and Red delicious, and a substantial increase was observed in Royal delicious peroxidase. Mg2+ inhibited the peroxidases from Golden delicious HP and Red delicious, but marginal activation was reported in peroxidases from Golden delicious JK and Royal delicious. Zn2+ established stimulation in Golden delicious HP and Golden delicious JK peroxidases, but inhibition was observed in peroxidases in Red delicious and Royal delicious. Methionine, proline, tryptophan, and valine stimulated all four apple peroxidases, but cysteine showed inhibition in Golden delicious JK.