• Journal of Mushroom
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• v.2 no.3
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• pp.127-139
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• 2004

Laccases are multicopper-containing enzymes which catalyze the oxidation of phenolic and nonphenolic compounds with the concomitant reduction of molecular oxygen. They often occur as isoenzymes, either constitutive or inducible, that oligomerize to multilateral complexes, what allow for penetration to the woody cell wall structure. White rot basidiomycete fungi may produce a number of laccase isoenzymes, some constitutively and others after induction. Fungal laccase is commonly induced by many ions, such as $Cu^{2+}$, $Cd^{2+}$ $Ca^{2+}$, $Li^+$, $Mn^{2+}$, $Ag^+$, $Hg^{2+}$, Mn and $Fe^{3+}$, phenolic compounds, some organic compounds, such as ethanol, isopropanol, cAMP, caffeine, p-anisidine, viscosinamide and paraquat, and nitrogens and even heat shock. A combination of Cu and pHB (p-hydroxybenzoic acid) made it possible to extend the inducible laccase activities over 30-fold. But the most effective inducer of laccase in the basidiomycete and other higher fungi is 2,5-xylidine, over 160-fold stimulation of laccase activity. The laccases are frequently encoded by gene families, as e.g. in Pycnoporus cinnabarinus, from which the lcc3-1 or the allelic form lac1 and lac3-2 have been cloned and sequenced. In the case of inducible forms the post-inductional laccase formation depends upon the synthesis of mRNA and the induction is due to the synthesis of a new protein.