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J. Bacteriol., Jul 1996, 4216-4223, Vol 178, No. 14
P Tomme, E Kwan, NR Gilkes, DG Kilburn and RA Warren
The cenC gene, encoding beta-1,4-glucanase C (CenC) from Cellulomonas fimi,
was overexpressed in Escherichia coli with a tac-based expression vector.
The resulting polypeptide, with an apparent molecular mass of 130 kDa, was
purified from the cell extracts by affinity chromatography on cellulose
followed by anion-exchange chromatography. N-terminal sequence analysis
showed the enzyme to be properly processed. Mature CenC was optimally
active at pH 5.0 and 45 degrees C. The enzyme was extremely active on
soluble, fluorophoric, and chromophoric glycosides (4-methylumbelliferyl
beta-glycosides, 2'-chloro-4'-nitrophenyl-beta-D- cellobioside, and
2'-chloro-4'-nitrophenyl-lactoside) and efficiently hydrolyzed
carboxymethyl cellulose, barley beta-glucan, lichenan, and, to a lesser
extent, glucomannan. CenC also hydrolyzed acid-swollen cellulose, Avicel,
and bacterial microcrystalline cellulose. However, degradation of the
latter was slow compared with its degradation by CenB, another C. fimi
cellulose belonging to the same enzyme family. CenC acted with inversion of
configuration at the anomeric carbon, in accordance with its classification
as a family 9 member. The enzyme released mainly cellobiose from soluble
cellodextrins and insoluble cellulose. Attack appeared to be from the
reducing chain ends. Analysis of carboxymethyl cellulose hydrolysis
suggests that CenC is semiprocessive enzyme with both endo- and
exoglucanase activities.
Copyright © 1996, American Society for Microbiology
Characterization of CenC, an enzyme from Cellulomonas fimi with both endo- and exoglucanase activities
Department of Microbiology, University of British Columbia, Vancouver, Canada.
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