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

Abstract

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.

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