Toggle Main Menu Toggle Search

Open Access padlockePrints

Cell, a noncellulosomal family 9 enzyme from Clostridium thermocellum, is a processive endoglucanase that degrades crystalline cellulose

Lookup NU author(s): Emeritus Professor Harry Gilbert


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


The family 9 cellulase gene cell of Clostridium thermocellum, was previously cloned, expressed, and characterized (G. P. Hazlewood, K. Davidson, J. I. Laurie, N. S. Huskisson, and H. J. Gilbert, J. Gen. Microbiol. 139:307-316, 1993). We have recloned and sequenced the entire cell gene and found that the published sequence contained a 53-bp deletion that generated a frameshift mutation, resulting in a truncated and modified C-terminal segment of the protein. The enzymatic properties of the wild-type protein were characterized and found to conform to those of other family 9 glycoside hydrolases with a so-called theme B architecture, where the catalytic module is fused to a family 3c carbohydrate-binding module (CBM3c); Cell also contains a C-terminal CBM3b. The intact recombinant Cell exhibited high levels of activity on all cellulosic substrates tested, with pH and temperature optima of 5.5 and 70°C, respectively, using carboxymethylcellulose as a substrate. Native Cell was capable of solubilizing filter paper, and the distribution of reducing sugar between the soluble and insoluble fractions suggests that the enzyme acts as a processive cellulase. A truncated form of the enzyme, lacking the C terminal CBM3b, failed to bind to crystalline cellulose and displayed reduced activity toward insoluble substrates. A truncated form of the enzyme, in which both the cellulose-binding CBM3b and the fused CBM3c were removed, failed to exhibit significant levels of activity on any of the substrates examined. This study underscores the general nature of this type of enzymatic theme, whereby the fused CBM3c plays a critical accessory role for the family 9 catalytic domain and changes its character to facilitate processive cleavage of recalcitrant cellulose substrates.

Publication metadata

Author(s): Gilad R, Rabinovich L, Yaron S, Bayer EA, Lamed R, Gilbert HJ, Shoham Y

Publication type: Article

Publication status: Published

Journal: Journal of Bacteriology

Year: 2003

Volume: 185

Issue: 2

Pages: 391-398

Print publication date: 01/01/2003

ISSN (print): 0021-9193

ISSN (electronic): 1067-8832

Publisher: American Society for Microbiology


DOI: 10.1128/JB.185.2.391-398.2003

PubMed id: 12511483


Altmetrics provided by Altmetric