Purification and determination of some biochemichal properties of polyphenol oxidase from tea plant

This research was undertaken to determine some of the biochemical properties (substrate specificity, optimum pH, optimum temperature, heat inactivation, and effect of inhibitors) of polyphenol oxidase (PPO) which was isolated from fresh tea leaves and partially purified.Of the substrates tested, the best substrate for PPO was 4-methylcatechol. The optimum pH for PPO activity was found to be 6.02 and the enzyme showed high activity over a broad pH range of 4.03-7.00. The optimum temperature for PPO activity was 30°C. Enzyme activity was more than 70% between 20-80°C. According to thermal inactivation studies, kD values increased as the temperature increased whereas half-life and D values decreased. Energy of activation (Ea) and Z values were found to be 58.301 kj/mol (r²=0.9614) and 39.68 °C (r²=0.9645), respectively. The enzyme is thermo-stable. Of the inhibitors tested, L-cysteine was the least effective inhibitor.