The second cupredoxin domain of the plant laccases
Laccase is a blue multi-copper enzyme that catalyzes the oxidation of a variety aromatic - notably phenolic and inorganic substances coupled to the reduction of molecular oxygen to water. Laccase has been implicated in a wide spectrum of biological activities and, in particular, plays a key role in morphogenesis, development and lignin metabolism. Plants usually express multiple laccase genes, but their precise physiological/biochemical roles remain largely unclear. Like other related multicopper oxidases (MCOs), laccase is composed of three cupredoxin domains that include one mononuclear and one trinuclear copper center. The copper ions are bound in several sites: Type 1, Type 2, and/or Type 3. The ensemble of types 2 and 3 copper is called a trinuclear cluster. MCOs oxidize their substrate by accepting electrons at a mononuclear copper center and transferring them to the active site trinuclear copper center. The cupredoxin domain 2 of 3-domain MCOs has lost the ability to bind copper.
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