. "Found in a broad variety of bacteria, fungi, plants, insects, crustaceans, and mammals, which is involved in the synthesis of betalains and melanin." . "The enzyme, which is activated upon binding molecular oxygen, can catalyze both a monophenolase reaction cycle or a diphenolase reaction cycle." . "During the monophenolase cycle, one of the bound oxygen atoms is transferred to a monophenol (such as L-tyrosine), generating an O-diphenol intermediate, which is subsequently oxidized to an o-quinone and released, along with a water molecule." . "The enzyme remains in an inactive deoxy state, and is restored to the active oxy state by the binding of a new oxygen molecule." . "During the diphenolase cycle the enzyme binds an external diphenol molecule (such as L-dopa) and oxidizes it to an O-quinone that is released along with a water molecule, leaving the enzyme in the intermediate met state." . "The enzyme then binds a second diphenol molecule and repeats the process, ending in a deoxy state." . "The second reaction is identical to that catalyzed by the related enzyme catechol oxidase (EC 1.10.3.1)." . "However, the latter can not catalyze the hydroxylation or monooxygenation of monophenols." . . . "Tyrosinase" . "Monophenol monooxygenase" . "Cresolase" . "Monophenol oxidase" . "N-acetyl-6-hydroxytryptophan oxidase" . "Phenolase" . "Tyrosine-dopa oxidase" . . "(1) 2 L-dopa + O(2) = 2 dopaquinone + 2 H(2)O." . "(2) L-tyrosine + O(2) = dopaquinone + H(2)O." . "Copper" .