Carbohydrate-binding modules: fine-tuning polysaccharide recognition

Abstract

The enzymic degradation of insoluble polysaccharides is one of the most important reactions on earth. Despite this, glycoside hydrolases attack such polysaccharides relatively inefficiently as their target glycosidic bonds are often inaccessible to the active site of the appropriate enzymes. In order to overcome these problems, many of the glycoside hydrolases that utilize insoluble substrates are modular, comprising catalytic modules appended to one or more non-catalytic CBMs (carbohydrate-binding modules). CBMs promote the association of the enzyme with the substrate. In view of the central role that CBMs play in the enzymic hydrolysis of plant structural and storage polysaccharides, the ligand specificity displayed by these protein modules and the mechanism by which they recognize their target carbohydrates have received considerable attention since their discovery almost 20 years ago. In the last few years, CBM research has harnessed structural, functional and bioinformatic approaches to elucidate the molecular determinants that drive CBM-carbohydrate recognition. The present review summarizes the impact structural biology has had on our understanding of the mechanisms by which CBMs bind to their target ligands.

Additional Carbohydrate-Binding Modules Enhance the Insoluble Substrate-Hydrolytic Activity of β-1,3-Glucanase from AlkaliphilicNocardiopsissp. F96

“…25) Type A CBMs contain planar hydrophobic ligand binding surfaces that interact with crystalline polysaccharides. Type B CBMs contain clefts that accommodate a single polysaccharide chain, while the ligand binding sites in type C CBMs interact with mono-, di-, or trisaccharides.…”

Understanding the structural and functional properties of carbohydrate esterases with a special focus on hemicellulose deacetylating acetyl xylan esterases

“…The pull-down assays conducted by Montanier et al (2009a) have showed that either CjCE2A or CjCE2B binds to the insoluble cellulose, and CE-2 enzymes of C. japonicus are not inhibited by the xylohexaose, cellohexaose and mannohexaose; isothermal titration calorimetry has supported these results as these enzymes does not bind to oligosaccharides (Montanier et al 2009a). Boraston et al (2004) have reported that aromatic side chains present in the catalytic sites of proteins play a crucial role in protein carbohydrate recognition (Boraston et al 2004). As the catalytic core domain of the CE class-2 enzymes is in the cleft which extends towards the catalytic domain, it constitutes to the substrate binding site of CE class-2 enzymes.…”

Enzymatic properties and primary structures of two α-amylase isozymes from the Pacific abalone Haliotis discus hannai

“…Prediction of secondary structure for the C-terminal region of HdAmy82 with GOR method (Garnier J et al, 1996) indicated that this region was made up of -sheets, turns, and random coils. This led us to consider that the C-terminal domain of HdAmy82 possesses somewhat similar structural motif to the known CBMs possessing a '-sandwich' motif (Boraston AB et al, 2004). To reveal the physiological rolls of the C-terminal ancillary domain of HdAmy82, studies on the recombinant HdAmy82 expressed with and without the C-terminal domain are expected.…”