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Logo of jbcThe Journal of Biological Chemistry
J Biol Chem. 2015 April 24; 290(17): 10587.
PMCID: PMC4409225

A Different Enzymatic Mechanism Found for Breaking Down Plant Cell Walls♦

Family 46 Carbohydrate-binding Modules Contribute to the Enzymatic Hydrolysis of Xyloglucan and β-1,3–1,4-Glucans through Distinct Mechanisms

♦ See referenced article, J. Biol. Chem. 2015, 290, 10572–10586

A challenge in the biofuel and biochemical industries is to find ways to efficiently and effectively break down the intricate cell walls of plants and algae to release energy and important biomolecules. Researchers are interested in a family of enzymes called CAZYmes (carbohydrate-active enzymes) because these enzymes can deconstruct cell walls. CAZYmes usually have a modular architecture that consists of a catalytic domain combined with one or more noncatalytic carbohydrate-binding modules (CBMs) that can function autonomously. In this Paper of the Week, a team led by Carlos M. G. A. Fontes at the University of Lisboa in Portugal and Harry Gilbert at Newcastle University presented biochemical, structural, and functional analyses of a unique CAZYme called endo-β-1,4-glucanase B (BhCel5B) from Bacillus halodurans. They found that, on its own, the CBM did not bind soluble or insoluble polysaccharides. The domain was tightly associated with the catalytic module. Depending on the nature of the carbohydrate, the CBM cooperated with the catalytic module to participate in substrate binding or target the enzyme to parts of the cell wall rich in polysaccharides. The authors say, “This report reveals the mechanism by which a CBM can promote enzyme activity through direct interaction with the substrate or by targeting regions of the plant cell wall where the target glucan is abundant.”

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Structure of BhCBM46.

Articles from The Journal of Biological Chemistry are provided here courtesy of American Society for Biochemistry and Molecular Biology