Carbohydrate active enzymes (CAZYmes) that target recalcitrant polysaccharides are modular enzymes containing noncatalytic carbohydrate-binding modules (CBMs) that direct enzymes to their cognate substrate, thus potentiating catalysis. The structure of Bacillus halodurans endo-beta-1,4-glucanase B (Cel5B) reveals that CBM46 is tightly associated with the catalytic module and, dependent on the glucan presented to the enzyme, can contribute directly to substrate binding or play a targeting role in directing the enzyme to regions of the plant cell wall rich in the polysaccharide hydrolyzed by the enzyme. The CBM46 domain displays a classic beta-sandwich jelly roll fold. Against beta-1,3-1,4-glucans CBM46 domain participates in productive substrate binding and thus plays a direct role in the hydrolytic activity of the enzyme [1].

1: Family 46 Carbohydrate-binding Modules Contribute to the Enzymatic Hydrolysis of Xyloglucan and beta-1,3-1,4-Glucans through Distinct Mechanisms. Venditto I, Najmudin S, Luis AS, Ferreira LM, Sakka K, Knox JP, Gilbert HJ, Fontes CM; J Biol Chem. 2015;290:10572-10586. PMID:25713075