Same enzymes of fungi are useful on one hand and harmful on other hand .disscus.
Answers
Fungal enzymes are too large to penetrate intact wood cell walls (Srebotnik and Messner, 1991). Therefore lignocellulose breakdown has been suggested to be initiated by low molecular weight (LMW) compounds that can readily penetrate into the wood and initiate wood decay (Goodell et al., 1997). LMWs include glycopeptides, phenolates or other iron-chelating compounds such as oxalate.
4.2 Fenton Chemistry
Fungi are also able to convert cellulose and lignin non-enzymatically by Fenton chemistry. Especially brown rot fungi use Fenton reactions in cellulose decomposition and lignin modification. In Fenton reactions hydroxyl radicals, which are the most reactive oxidants in nature, make wood fibers brittle. Hydroxyl radicals are produced by extracellular reduction of Fe (III) and O2. It has been also suggested that CDH and quinone redox cycling are sources of hydroxyl radicals (Hammel et al., 2002). Fungal alcohol oxidases produce hydrogen peroxide, which is required for the Fenton reactions. Hydrogen peroxide can also be formed from oxalic acid and peroxyls.
In addition to hydrogen peroxide, Fenton chemistry requires Fe2+ ions and acidic conditions, which are maintained by fungal secretion of protons and organic acids. The most common organic acid is oxalic acid, which is formed in fungal glyoxysomes and mitochondria as a citric acid cycle waste material (Mäkelä et al., 2010). Oxalate originated oxalate dianion is a significant chelator and solvent for metals which allows the fungal mycelium to reach and carry environmental cationic trace elements such as calcium, iron, manganese and magnesium ions. In Fenton reactions, oxalate as well as some fungal enzymes enable recycling of Fe2+ ions.