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Biochemical characterization and thermal inactivation of polyphenol oxidase from elephant foot yam (Amorphophallus paeoniifolius)

Singh, Anuradha, Wadhwa, Neeraj
Journal of food science and technology 2017 v.54 no.7 pp. 2085-2093
Amorphophallus paeoniifolius, EDTA (chelating agent), acetone, activation energy, ascorbic acid, bakery industry, calcium chloride, catechol, catechol oxidase, corms, endothermy, half life, heat inactivation, ion exchange chromatography, molecular weight, pH, sodium azide, sodium chloride, yams, zinc sulfate
Polyphenol oxidase from Amorphophallus corm was purified (5.54 fold) by acetone precipitation and ion exchange chromatography. Electrophoretic-blot analysis revealed that the molecular weight of enzyme is 40 kDa. Enzyme preferred catechol as substrate and showed optimum activity at pH 6 and 35 °C with Km of 17.56 mM and Vmax 0.023 U/ml/min. Thermal inactivation kinetics study showed that 5.68% inactivation was achieved at 75 °C within 40 min. The half-life time of PPO is between 126.00 and 32.54 min. The activation energy (Ea) and Z values are 64.22 kJ/mol and 34.01 °C, respectively. The inhibitory action of L-ascorbic acid, sodium azide, NaCl, CaCl₂, ZnSO₄ and EDTA were studied. Thermodynamic studies indicated a non-spontaneous (ΔG > 0) and endothermic reaction process. Other thermodynamic activation parameters, such as Ea, ΔH#, ΔG# and ΔS#, were also studied. Amorphophallus paeoniifolius polyphenol oxidase can find application in baking industry.