Identification of novel beta-mannan- and beta-glucan-binding modules: evidence for a superfamily of carbohydrate-binding modules.

Many glycoside hydrolases, which degrade long-chain carbohydrate polymers, possess distinct catalytic modules and non-catalytic carbohydrate-binding modules (CBMs). On the basis of conserved protein secondary structure, we describe here the identification and experimental characterization of novel type of mannanase-associated mannan-binding module and also characterization of two CBM family 4 laminarinase-associated beta-glucan-binding modules. These modules are predicted to belong to a superfamily of CBMs which include families 4, 16, 17, 22 and a proposed new family, family 27.