Enzyme Degrades Lignin

Biological Strategy

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Chemically Break Down Organic Compounds

The vast majority of biochemical assembly and breakdown processes–even by the most complex organisms–occur within cells. In fact, cells are able to perform hundreds, even thousands of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). Part of the reason that decomposition reactions (chemical breakdown) can occur under such mild conditions is because most often, they occur in a stepwise, enzyme-mediated fashion, sipping or releasing small amounts of energy at each step. For example, the breakdown of glucose to pyruvate–and the release of energy–occurs in the 10-step enzyme catalyzed process of glycolysis.

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Chemically Break Down Inorganic Compounds

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Chemically Generate Flow of Electrons (Redox)

Electron flows, or electron transport, is a critical step in numerous biochemical pathways. For example, the flow of electrons along the electron transport chain between membrane-bound proteins of mitochondria during cellular respiration or the chloroplast during photosynthesis triggers a flow of protons across the same membrane. This flow provides the energy for cellular processes similar to the flow of water across a hydroelectric dam.

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Basidiomycetes (Club fungi)

Division Basidiomycota (“club fungi”): Mushrooms, smuts, rusts

Basidiomycota are the iconic group of organisms that comprises up to one-third of all fungi: 16 classes, 1,589 genera, and about 30,000 species. Basidiomycota is the second largest group of fungi next to Ascomycota, the sac fungi known as molds, yeasts, and powdery mildews. Basidiomycota hold a worldwide importance in food, culture, folklore, and medicine. Most club fungi reproduce through spores, while a small group can reproduce asexually. While many mushrooms are foraged and eaten by people, some can produce deadly toxins and hallucinogens. Psilocybin mushrooms produce hallucinogenic toxins which hold some potential for the treatment of mental health disorders.

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Laccase enzymes of Trametes fungi catalyze the oxidation of organic and inorganic substrates including lignin through direct electron transfer.

“First of all, high-redox-potential laccases are able to oxidize both high- and low-redox-potential substrates, which significantly broadens the degradation ability of the fungi at the beginning of their growth. Secondly, for all high-redox-potential laccases, bioelectroreduction of oxygen on the carbon electrode based on direct electron transfer reactions between the electrode (solid substrate) and the enzymes has been shown, including the two laccases studied in the present work. Indeed, not only laccase, but also all ligninolytic enzymes from white rot fungi (lignin and manganese peroxidases, laccase, and cellobiose dehydrogenase) display the phenomenon of direct electron transfer.” (Shleev et al. 2007:46)

Last Updated August 18, 2016

References

Journal article

Characterization of two new multiforms of Trametes pubescens laccase

Shleev, S.; Nikitina, O.; Christenson, A.; Reimann, C. T.; Yaropolov, A. I.; Ruzgas, T.; Gorton, L.

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