Partial Purification And Characterization Of Polyphenol Oxidase From Wild Pears (Pyrus communis)

ABSTRACT: precipitation, dialysis and ion exchange chromatography. Of the substrates tested, pyrogallol was the better substrate for PPO with a Km value of 8.7 mM at pH 5 and catechol is better with Km value 4.7 mM at pH 7. The enzyme showed high activity over a broad pH range of 4 – 8 so the optimum pH for PPO activity was found to be 5 and 7. The optimal temperature for enzyme activity was found to be 45°C in presence of pyrogallol but 55°C with catechol as substrate at pH 7. Km value for wild pear PPO is calculated 9.5 and 4.7 mM for catechol and 8.7 and 5.1 mM for pyrogallol at pHs 5 and 7 respectively. As can be seen, affinity of PPOs for various substrates varies widely.The enzyme showed a broad activity over a broad pH and temperature range. The thermal inactivation studies showed that the enzyme is heat resistant. The enzyme showed the highest activity toward pyrogallol and no activity toward tyrosine. Of the inhibitors tested, the most potent inhibitors was sodium kojic acid.