Characteristics of Polyphenol Oxidase in Hale Haven Paches

Authors : Ahmet YEMENİCİOĞLU, Bekir CEMEROĞLU

Pages : 261-266

View : 22 | Download : 12

Publication Date : 1998-12-01

Article Type : Research Paper

Abstract :The characteristics of polyphenol oxidase insert ignore into journalissuearticles values(PPO); from `Hale Haven` peaches were investigated. `Aceton Powder` was first prepared from peaches at three different maturity stages, namely unripe, half-ripe and fully ripe. The optimum pH, Michaelis costant insert ignore into journalissuearticles values(Km);, maximum velocity insert ignore into journalissuearticles values(Vmax); as well as thermal inactivation of enzyme activity were studied with the enzyme solution prepared form `Aceton Powder`. According to the degree of maturity, the pH optimum of PPO was between 6.0 and 6.5. The enzyme from fully ripe peaches showed a Km of 14.3 mM for catechol and Wmax of 1.25 OD min -1 mL -1 at pH 6.8. The termal inactivation kinetics of enzyme was studied at 70 o C. The heat inactivation curve for each enzyme extract consisted of an inital steep straight line, and a final straight line with a shallow slope. It was therefore concluded that two isoenzymes of PPO with different resistances were present in peaches. The inital line represented inactivation of heat-labile enzyme and second heat-resist-ant enzyme. The inactivation of the heat-resistant fraction at 70 o C followed a first order reaction kinetics. The rate constants were 20.36, 23.17 and 19.66.10 -2 .min -1 for unripe, half-ripe and fully ripe peaches, respectively. The proportion of heat-resistant portion in total activity was estimated by extrapolating the heat resistant curve to zero time. These values were 83%, 48% and 55% of total enzyme activity for unripe, half-ripe und fully ripe fruit, respectively.
Keywords : Turk J Agric For, 22, 1998, 261 266 Turk J Agric For, vol 22, iss 3