Carbohydrate-binding domains: multiplicity of biological roles

Abstract

Insoluble polysaccharides can be degraded by a set of hydrolytic enzymes formed by catalytic modules appended to one or more non-catalytic carbohydrate-binding modules (CBM). The most recognized function of these auxiliary domains is to bind polysaccharides, bringing the biocatalyst into close and prolonged vicinity with its substrate, allowing carbohydrate hydrolysis. Examples of insoluble polysaccharides recognized by these enzymes include cellulose, chitin, beta-glucans, starch, glycogen, inulin, pullulan, and xylan. Based on their amino acid similarity, CBMs are grouped into 55 families that show notable variation in substrate specificity; as a result, their biological functions are miscellaneous. Carbohydrate or polysaccharide recognition by CBMs is an important event for processes related to metabolism, pathogen defense, polysaccharide biosynthesis, virulence, plant development, etc. Understanding of the CBMs properties and mechanisms in ligand binding is of vital significance for the development of new carbohydrate-recognition technologies and provide the basis for fine manipulation of the carbohydrate-CBM interactions.

Fungal lytic polysaccharide monooxygenases bind starch and β‐cyclodextrin similarly to amylolytic hydrolases

“…Typically, glycoside hydrolases (GHs) that degrade complex polysaccharides possess carbohydrate-binding modules (CBMs) that promote enzyme-substrate proximity and thereby enhance catalytic efficiency [16,17]. Moreover, CBMs can also modulate the specificity and activity of cognate enzymes against plant cell wall Abbreviations AA, auxiliary activity; CAZy, carbohydrate-active enzymes; CBM, carbohydrate-binding module; DSC, differential scanning calorimetry; GH, glycoside hydrolase; ITC, isothermal titration calorimetry; LPMO, lytic polysaccharide monooxygenase; SBS, starch-binding site; SDS/PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; b-CD, b-cyclodextrin.…”

“…Many industrial applications require the disruption of starch granules through hydrothermal, harsh chemical, or enzymatic treatments [11][12][13]. Despite development of relatively efficient a-amylases and other starch-degrading enzymes, there is still a significant margin for improving starch hydrolysis yields and shortening processing time, which would significantly reduce energy and costs of the process [14,15].Typically, glycoside hydrolases (GHs) that degrade complex polysaccharides possess carbohydrate-binding modules (CBMs) that promote enzyme-substrate proximity and thereby enhance catalytic efficiency [16,17]. Moreover, CBMs can also modulate the specificity and activity of cognate enzymes against plant cell wall Abbreviations AA, auxiliary activity; CAZy, carbohydrate-active enzymes; CBM, carbohydrate-binding module; DSC, differential scanning calorimetry; GH, glycoside hydrolase; ITC, isothermal titration calorimetry; LPMO, lytic polysaccharide monooxygenase; SBS, starch-binding site; SDS/PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; b-CD, b-cyclodextrin.…”

Polysaccharide-synthesizing Glycosyltransferases and Carbohydrate Binding Modules: the case of Starch Synthase III

“…However, CBM20 and CBM21 families are proposed to form a common clan [23]. Analyses of threedimensional structures from many of these families showed a characteristic SBD fold of a distorted -barrel composed of several -strands and with one or, more frequently, two distinct binding sites that exhibit site-dependent modes of carbohydrate binding [25,26,[41][42][43].…”

Two structurally related starch-binding domain families CBM25 and CBM26

“…Both families adopt a typical SBD fold (Boraston et al 2004;Guillen et al 2010) of distorted β-barrel (a β-sandwich) formed by 9 or 10 β-strands, as shown for solved three-dimensional structure of both modules present in the family GH13 maltohexaoseproducing amylase from Bacillus halodurans (Boraston et al 2006).…”