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X4 modules represent a new family of carbohydrate-binding modules that display novel properties

Lookup NU author(s): Dr David Bolam, Gavin Pell, Deborah Hogg, Greta Galbraith, Emeritus Professor Harry Gilbert


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The hydrolysis of the plant cell wall by microbial glycoside hydrolases and esterases is the primary mechanism by which stored organic carbon is utilized in the biosphere, and thus these enzymes are of considerable biological and industrial importance. Plant cell wall-degrading enzymes in general display a modular architecture comprising catalytic and non-catalytic modules. The X4 modules in glycoside hydrolases represent a large family of non-catalytic modules whose function is unknown. Here we show that the X4 modules from a Cellvibrio japonicus mannanase (Man5C) and arabinofuranosidase (Abf62A) bind to polysaccharides, and thus these proteins comprise a new family of carbohydrate-binding modules (CBMs), designated CBM35. The Man5C-CBM35 binds to galactomannan, insoluble amorphous mannan, glucomannan, and manno-oligosaccharides but does not interact with crystalline mannan, cellulose, cello-oligosaccharides, or other polysaccharides derived from the plant cell wall. Man5C-CBM35 also potentiates mannanase activity against insoluble amorphous mannan. Abf62A-CBM35 interacts with unsubstituted oat-spelt xylan but not substituted forms of the hemicellulose or xylo-oligosaccharides, and requires calcium for binding. This is in sharp contrast to other xylan-binding CBMs, which interact in a calcium-independent manner with both xylo-oligosaccharides and decorated xylans.

Publication metadata

Author(s): Bolam DN, Xie H, Pell G, Hogg D, Galbraith G, Henrissat B, Gilbert HJ

Publication type: Article

Publication status: Published

Journal: Journal of Biological Chemistry

Year: 2004

Volume: 279

Issue: 22

Pages: 22953-22963

ISSN (print): 0021-9258

ISSN (electronic): 1083-351X

Publisher: American Society for Biochemistry and Molecular Biology


DOI: 10.1074/jbc.M313317200

PubMed id: 15004012


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