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Two noncellulosomal cellulases of Clostridium thermocellum, Cel9I and Cel48Y, hydrolyse crystalline cellulose synergistically

Author:
Berger, Emanuel, Zhang, Dong, Zverlov, Vladimir V., Schwarz, Wolfgang H.
Source:
FEMS microbiology letters 2007 v.268 no.2 pp. 194-201
ISSN:
0378-1097
Subject:
Clostridium thermocellum, barley, xylanases, cellulosome, chitinase, carboxymethylcellulose, genes, hydrolysis, amylases, synergism, endo-1,4-beta-glucanase, beta-glucans, Escherichia coli
Abstract:
The genome of Clostridium thermocellum contains a number of genes for polysaccharide degradation-associated proteins that are not cellulosome bound. The list includes β-glucanases, glycosidases, chitinases, amylases and a xylanase. One of these 'soluble'-enzyme genes codes for a second glycosyl hydrolase (GH)48 cellulase, Cel48Y, which was expressed in Escherichia coli and biochemically characterized. It is a cellobiohydrolyse with activity on native cellulose such as microcrystalline and bacterial cellulose, and low activity on carboxymethylcellulose. It is about 100 times as active on amorphic cellulose and mixed-linkage barley β-glucan compared with cellulase Cel9I. The enzyme Cel48Y shows a distinct synergism of 2.1 times with the noncellulosomal processive endoglucanase Cel9I on highly crystalline bacterial cellulose at a 17-fold excess of Cel48Y over Cel9I. These data show that C. thermocellum has, besides the cellulosome, the genes for a second cellulase system for the hydrolysis of crystalline cellulose that is not particle bound.
Agid:
2537804