Characterization of polyphenol oxidase from white cherry fruit

This research was undertaken to determine some of the biochemical properties (optimum pH, optimum temperature, heat inactivation, kinetic parameters and effect of inhibitors) of polyphenol oxidase (PPO) which was isolated from white cherry grown in Ereğli/Konya and partially purified.The enzyme showed two peaks with PPO activity, which were denoted as isoenzyme A and isoenzyme B. The isoenzyme A and isoenzyme B were purified 3.9 fold with a recovery of 48.7% and 76.7 fold with a recovery of 54.3%, respectively. The optimum pH value for isoenzyme A was 4.5 and 4.98 for isoenzyme B. The temperature optima for enzyme activity were found to be 20°C for isoenzyme A and 30°C for isoenzyme B. The affinity of isoenzyme B for catechol as substrate was higher than that of isoenzyme A. Activation energies(Ea) and Z values were 22.1°C (r²=0.8832) and 98.5 kj.mol-1 (r²=0.8776) for isoenzyme A and 13.9°C (r²=0.9903) and 157.1 kj.mol-1 (r²=0.9886) for isoenzyme B, respectively. L-cysteine and sodium disulphide were used as inhibitors. It was found that the effects of the inhibitors differed from each other and both inhibitors inhibited both isoenzymes 100% at 1.00 mM.