Lignin-modifying enzymes (LMEs) are various types of enzymes produced by fungi and bacteria that catalyze the breakdown of lignin, a biopolymer commonly found in the cell walls of plants. The terms ligninases and lignases are older names for the same class, but the name "lignin-modifying enzymes" is now preferred, given that these enzymes are not hydrolytic but rather oxidative (electron withdrawing) by their enzymatic mechanisms. LMEs include peroxidases, such as lignin peroxidase (EC 1.11.1.14), manganese peroxidase (EC 1.11.1.13), versatile peroxidase (EC 1.11.1.16), and many phenoloxidases of the laccase type.
LMEs have been known to be produced by many species of white rot basidiomycetous fungi, including: Phanerochaete chrysosporium, Ceriporiopsis subvermispora, Trametes versicolor, Phlebia radiata, Pleurotus ostreatus and Pleurotus eryngii.
LMEs are produced not only by wood-white rotting fungi but also by litter-decomposing basidiomycetous fungi such as Agaricus bisporus (common button mushroom), and many Coprinus and Agrocybe species. The brown-rot fungi, which are able to colonize wood by degrading cellulose, are only able to partially degrade lignin.
Some bacteria also produce LMEs, although fungal LMEs are more efficient in lignin degradation. Fungi are thought to be the most substantial contributors to lignin degradation in natural systems.[1]
LMEs and cellulases are crucial to ecologic cycles (for example, growth/death/decay/regrowth, the carbon cycle, and soil health) because they allow plant tissue to be decomposed quickly, releasing the matter therein for reuse by new generations of life. LMEs are also crucial to a number of different industries.