Polyphenol oxidase activity of oregano at different stages

The effects of pH and temperature on polyphenol oxidase (PPO) activity of organs such as root, stem and leaf, of Origanum vulgare ssp. hirtum, collected at different stages (vegetative and generative) and from various localities around Balikesir, Turkey, were investigated using catechol as a substrate. PPO obtained from organs of Origanum was partially purified by (NH4)(2)SO4 precipitation, followed by dialysis. The PPO activities of organs of Origanurn varied among the different localities and between the different stages, and leaf had the highest PPO activity, followed by stem and root, in both stages. Optimum pH of Origanum in the transition from the vegetative stage to the generative stage decreased by 0.4 of a unit, approximately, whereas optimum pHs of Origanum-PPO collected from various localities were closely similar. Optimum temperature decreased very little in the transition from the vegetative stage to the generative stage. Activation energy values were calculated from the Arrhenius equation. (C) 2004 Elsevier Ltd. All rights reserved.