Laccase

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Laccases (EC 1.10.3.2) are copper-containing oxidase enzymes that are found in many plants, fungi, and microorganisms. The copper 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). Laccases act on phenols and similar molecules, performing a 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 lignols, a family of naturally occuring phenols.^[1] Laccases can be polymeric, and the enzymatically active form can be a dimer or trimer.

The tricopper site found in many laccases, notice that each copper center is bound to imidazole (color code: copper is brown, nitrogen is blue).

The easiest way to detect activity in laccases is with a spectrophotometrically. Substrates that are commonly used with this method are 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.

[edit] Applications and potential utility

Laccases have been examined as cathode in an enzyme catalyzed fuel cell. They can be paired with an electron mediator to facilitate electron transfer to a solid electrode wire.

Laccase is one of the few oxidoreductases commercialized as industrial catalysts. The enzyme can be used for textile dyeing/finishing, wine cork making, and many other industrial, environmental, diagnostic, and synthetic uses (see, e.g., Feng Xu, (2005) Applications of oxidoreductases: Recent progress, Industrial Biotechnology 1, 38-50[1]).