Polyphenoxidase from Six Mature Grape Varieties and Their Activities towards Various Phenols

概要

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Juices were prepared from three white and three and grape varieties harvested at full maturity and comparative studies on their oxygen-uptake, abosorbance at 420 nm (degree of browning), polyphenoloxidase (EC 1.10.3.1; PPO) activity, and their phenol compositions were done. There was no correlation among the amounts of oxygen-uptake and oxidizable phenols in the juices and their degree of browning. However, there was similarity among the PPO from the six grape varieties in their general enzymatic properties and substrate specificity towards twenty-five phenols. A partially purified PPO fraction from Koshu juice, which did not contain free phenols, showed strong activity towards (+)-catechin, (-)-epicatechin, caffeic acid, catechol, pyrogallol, and protocatechuic acid (oxidizable phenols), but had no activity towards the other fifiteen phenols. The oxidizable substrates were not always the only limiting factor in the oxidation and browning phenols by the PPO. Some unoxidizable phenols such as gallic acid, p-cresol, and tannic acid which were not substrates for PPO inhibited the oxidation of the oxidizable phenols except pyrogallol which was not inhibited by gallic acid. On the other hand, hydroquinone promoted the oxidation of the oxidizable phenols except protocatechuic acid. These showed that there were competitive reactions and synergism during the enzymatic oxidation of phenols.
公益社団法人日本生物工学会の論文
1991-03-25