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"Lignin-modifying enzymes"

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 white rot 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.

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.

Bacterial lignin-modifying enzymes

Although much research has been done to understand fungal LMEs, only recently has more focus been placed on characterizing these enzymes in bacteria. The main LMEs in both fungi and bacteria are peroxidases and laccases.

Although bacteria lack homologs to the most common fungal peroxidases (lignin peroxidase, manganese peroxidase, and versatile peroxidase), many produce dye decolourizing peroxidases (DyP-type peroxidases). Bacteria from a variety of classes express DyP peroxidases, including Gammaproteobacteria, Firmicutes, and Actinobacteria. Peroxidases depolymerize lignin by oxidation using hydrogen peroxide. Fungal peroxidases have higher oxidizing power than bacterial DyP-type peroxidases studied so far, and are able to degrade more complex lignin structures. DyP-type peroxidases have been found to work on a large range of substrates, including synthetic dyes, monophenolic compounds, lignin-derived compounds, and alcohols.

Laccases, which are multicopper oxidases, are another class of enzymes found in both bacteria and fungi which have significant lignin-degrading properties. Laccases degrade lignin by oxidation using oxygen. Laccases are also widely distributed among bacterial species, including Bacillus subtilis, Caulobacter crescentus, Escherichia coli and Mycobacterium tuberculosum. Like DyP-type peroxidases, bacterial laccases have a wide substrate range.

There is interest in using bacterial laccases and DyP peroxidases for industry applications, biotechnology and bioremediation because of the greater ease of manipulation of bacterial genomes and gene expression compared to fungi. The wide range of substrates for these types of enzymes also increases the range of processes they may be used in. These processes include pulp processing, textile dye modification, decontamination of waste water and production of pharmaceutical building blocks. Furthermore, bacterial laccases function at higher temperatures, alkalinity, and salt concentrations than fungal laccases, making them more suitable for industrial use.

Both intracellular and extracellular bacterial DyP-type peroxidases and laccases have been identified, suggesting that some are used as intracellular enzymes while others are secreted to degrade compounds in the environment. However, their roles in bacterial physiology and their natural physiological substrates have yet to be detailed.

Osolodova (talk) 01:11, 20 November 2017 (UTC)

Assignment 3: Article Edit

Original: "Lignin-modifying enzyme"

Lignin-modifying enzymes (LMEs) are various types of enzymes produced by fungi 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 so-called 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 not able to produce LMEs.

Some results on LME-type of peroxidases have also been reported for some species of filamentous bacteria such as Streptomyces viridosporus T7A, Streptomyces lavendulae REN-7 and Clostridium stercorarium.

However, efficient lignin and lignin-like polymer degradation is only achieved by fungal LME peroxidases, and laccases in combinations with organic charge transfer mediator compounds. Laccases are more widely distributed enzymes belonging to the multicopper oxidase (MCO) superfamily encompassing all three domains of life (bacteria, archaea, eukarya).

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.

Edits - "Lignin-modifying enzyme"

Bacterial Lignin-modifying Enzymes

Although much research has been done to understand fungal LMEs, only recently has more focus been placed on characterizing these enzymes in bacteria. Most LMEs are peroxidases, and although bacteria generally lack homologs to the most common fungal LMEs, they are rich in another type of peroxidase - dye decolourizing peroxidases (DyP-type peroxidases). The first enzyme belonging to this family was characterized in fungi in 1999 as a dye-degrading enzyme before bacterial counterparts were discovered. Bacteria from a variety of phyla express DyP peroxidases, including Gammaproteobacteria, Firmicutes, and Actinobacteria.

Both intracellular and extracellular bacterial DyP-type peroxidases have been identified, suggesting that some are used as intracellular enzymes while others are secreted to degrade compounds in the environment. DyP-type peroxidases have been found to work on a large range of substrates, including synthetic dyes, monophenolic compounds, lignin-derived compounds, and alcohols. However, their roles in bacterial physiology and their natural physiological substrates have yet to be detailed.

Although fungal counterparts of bacterial DyP-type peroxidases have more potency in terms of their lignin-degradation ability, bacterial DyP-type peroxidases have more potential for industry applications since manipulating genomes and gene expression in fungi is much more complicated than in bacteria.

Laccases, which are multicopper oxidases, are another class of enzymes found in both bacteria and fungi which have significant lignin-degrading properties. Like bacterial DyP-type peroxidases, bacterial laccases have yet to be fully understood and characterized. There is also interest in using these for industry applications, biotechnology and bioremediation because they have stronger degradation ability compared to DyP-type peroxidases and also have a wide substrate range. Again, laccases of bacterial origin show more potential for applications due to greater ease of manipulation.

Osolodova (talk) 21:42, 8 October 2017 (UTC)