Chitosanase families




THE FAMILY GH7

The the family 7 of glycoside hydrolases includes enzymes with diversified substrates specificities. Besides chitosanases it includes endo-β-1,4-glucanases, reducing end-acting cellobiohydrolases and endo-β-1,3-1,4-glucanases. So far, near 5000 sequences have been classified in the family 7 of glycoside hydrolases.

Some hydrolases from family 7 have both chitosanase and cellulase activities. In 2007, Ike et al. (119) have found that an enzyme produced by the filamentous fungus Trichoderma reesei (anamorph of Hypocrea jecorina) has both chitosanase and cellobiohydrolase activities. The same was true for another fungal hydrolase secreted by Aspergillus aculeatus. Analysis of reaction products suggested that these two enzymes, named AaCBHI and TrCBHI respectively, act on soluble chitosan as endo-hydrolases. The latter also cleaves cellulose in a processive way from the reducing end, to produce cellobiose. The CCBE cellulase produced by the ascomycete Trichoderma viride, is another bifunctional chitosanase-chitobiohydrolase that belongs to GH7 family (116). Analysis of the products of degradation of chitosan suggests that CCBE acts, at first, via an endohydrolytic mode, causing the release of chitobiose, of chitotriose, of chitotetraose and some larger chitooligosaccharides, and then operates in exohydrolytic mode while releasing glucosamine monomers and small chitooligosaccharides.



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This page was created by Ryszard Brzezinski, Marie-Ève Lacombe-Harvey and Andrzej Neugebauer.
Questions? Proposals? Comments? Write to Ryszard.Brzezinski@USherbrooke.ca
Last updated: November 2013