Research Information System
The International Enzyme Enginnering Symposium, Aydın, Turkey, vol.1, pp.67
Polyphenol oxidase (PPO, EC:1.14.18.1) is a copper enzyme which catalyzes two different reactions in the presence of oxygen: the hydroxylation of monophenol to o-diphenols (monophenolase activity) and the oxidation of o-diphenols to o-quinones (dipbenolase activity) which, in turn, are polymerized to brown, red, or black pigments. PPOs are essential for melanization [1]. PPO and phenolics are directly responsible for some of the enzymatic browning in fruits and vegetables. It has been reported that levels of PPO and phenolics may change during fruit development and ripening which may influence the potential damage in loquat fruit [2].
Polyphenol oxidase (PPO) was extracted from eggplant cultivar (Solanum melongena L. 'kadife'), collected from several fields in Trabzon (Turkey), during fruit ripening and its partial biochemical characteristics were studied in the present study. Extracts were prepared from fruits at three different maturity stages, namely unripe (stage 1), half ripe (stage 2) and fully ripe (stage 3). Substrale specificity, oplimum pH, temperalure, enzyme and substrate concentralion and tolal phenolic conlenls were determined. PPO showed activily using the subsrates catechol, 4-melhylcatechol and l-tyrosine, but no aclivity PHPPA. The higheslPPO activily was recorded in l-DOPA as subslrale for all slages. The optimum pH for the cultivar (cv.) PPO activity was pH 7.0 Ihroughout the maturity slages, and the optimum temperature was found 20, 20 and 10 °C, respeclively, for each stage. The substrale concentralions optima of the cullivar were 20 mM for Ihe slages 1 and 3, and 10 mM for the slage 2. The total phenolic canIenIs of the fruits through the maturity stages were 49.8 ± 0.8mg/g, 49.8 ± 1.8 mg/g and 36,9 ± 0.2 mg/g, respeclively. A correlation in the enzyme activity and the phenolic contenIs are also investigaled.