RESUMO
Peroxidase (POD) from jackfruit bulb was purified using ammonium sulfate precipitation, hydrophobic interaction and gel filtration columns. The POD was a dimer with a molecular weight of 104kDa. The Km and Vmax values for guaiacol, gallic acid and ophenylenediamine (OPD) were estimated. OPD was the most suitable substrate. The enzyme showed its maximum activity at pH5.5 and 55-60°C. The activation energy (Ea) of heat inactivation was estimated to be 206.40kJ/mol. The enthalpy, free energy and entropy values for the thermal inactivation were also determined. The POD activity was enhanced by K+, Zn2+, Ba2+, citric acid, malic acid, benzoic acid and EDTA·Na2, but inhibited by Cu2+, Ca2+, glutathione, cysteine and ascorbic acid. Chemical modification indicated a histidine residue was located in the enzyme active site. The POD activity in fruit extracts significantly decreased when heated at 80°C and 90°C. The ferric-reducing antioxidant power, ABTS radical scavenging activity and total phenolics decreased with increasing heating temperature and time.
