lakkases

Laccases are multicopper oxidase enzymes that catalyze the oxidation of a broad range of phenolic and non-phenolic substrates, using molecular oxygen as the terminal electron acceptor and reducing it to water. They occur in a variety of organisms, most notably in fungi, where they play a central role in lignin modification and degradation, but they are also found in plants and certain bacteria.

Structurally, laccases contain four copper ions organized into three distinct redox centers: a type 1 (blue) copper center that accepts electrons from the substrate, and a type 2/type 3 binuclear center where molecular oxygen is reduced to water. Electron transfer from the substrate to the type 1 copper center is coupled to reduction at the trinuclear copper cluster, completing the catalytic cycle. The enzymes are typically glycosylated and secreted in many fungi, enabling extracellular oxidation of substrates.

Substrate scope is broad and includes diphenols, polyphenols, anilines, and other aromatic compounds. In many practical applications, laccases act in conjunction with redox mediators, small molecules that shuttle electrons between the enzyme and substrates that are not readily oxidized by the active site. This mediator-assisted mechanism expands utility in bioremediation, textile dye decolorization, and organic synthesis.

Biological roles include lignin remodeling in wood-decaying fungi, pigment formation in plants, and defense-related oxidation reactions. Industrial applications exploit laccases for environmental cleanup, biosensors, and sustainable chemistry. Production methods range from native extraction to recombinant expression in yeasts or filamentous fungi, with ongoing improvements in stability, pH dependence, and substrate range.