Laccases (EC 1.10.3.2) are copper-containing oxidase enzymes found in many plants, fungi, and microorganisms. Laccases act on phenols and similar molecules, performing one-electron oxidations, which remain poorly defined. It is proposed that laccases play a role in the formation of lignin by promoting the oxidative coupling of monolignols, a family of naturally occurring phenols. Laccases can be polymeric, and the enzymatically active form can be a dimer or trimer. Other laccases, such as those produced by the fungus Pleurotus ostreatus, play a role in the degradation of lignin, and can therefore be classed as lignin-modifying enzymes.

Laccases require oxygen as a second substrate for their enzymatic action.

Spectrophotometry can be used to detect laccases, using the substrates ABTS, syringaldazine, 2,6-dimethoxyphenol, and dimethyl-p-phenylenediamine. Activity can also be monitored with an oxygen sensor, as the oxidation of the substrate is paired with the reduction of oxygen to water.

Laccase was first studied by Gabriel Bertrand in 1894 in the sap of the Chinese lacquer tree, where it helps to form lacquer, hence the name laccase.

Laccases can catalyze ring cleavage of aromatic compounds.

The copper bound by laccase is 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 (see figure). Type 1 copper is available to action of solvents, such as water. It can be displaced by mercury, substituted by cobalt or removed via a copper complexone. Removal of type 1 copper causes a decrease in laccase activity. Cyanide can remove all copper from the enzyme, and re-embedding with type 1 and type 2 copper has been shown to be impossible. Type 3 copper, however, can be re-embedded back into the enzyme.

...
Wikipedia