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Polyphenol oxidase

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A copper-containing enzyme that catalyzes the o-hydroxylation of monophenols to o-diphenols, as well as the oxidation of o-diphenols to o-quinones.


This enzyme is found commonly in fruits. It is responsible for the fruits to turn brown. The rapid polymerization of o-quinones results in the formation of black, brown or red pigments (polyphenols), which cause fruit browning.

Tyrosine may also be oxidized by the action of polyphenol oxidase to form o-quinone. Hence, polyphenol oxidase may also be referred to as tyrosinase.

Word origin: Greek, polýs, many + phenol.

Abbreviation: POP


See also: phenol oxidase.