Abstract
CbhA and CelK are family-9 glycosyl hydrolases (β-1,4-glucanase) isolated from the bacterium Clostridium thermocellum.1 The members of the glycosyl hydrolase (GH) family-9 have been almost exclusively endocellulolytic, with a few being processive endoglucanses (enzymes demonstrating both endo- and exocellulolytic activity).2 CbhA and CelK are the only members of the family reported to be solely exohydrolytic. We report activity assays on various substrates, soluble to insoluble reducing sugar assays, viscosity measurements, and thinlayer chromatography product analysis, which all showed that the truncated CbhA, expressed in E. coli, acts as an endocellulase, like most other family-9 glycosyl hydrolases.
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