Carbohydrate Binding Module 6 (CBM6); many are appended to glycoside hydrolase (GH) family 11 and GH43 xylanase domains. This family includes carbohydrate binding module 6 (CBM6) domains that are appended mainly to glycoside hydrolase (GH) family domains, including GH3, GH11, and GH43 domains. These CBM6s are non-catalytic carbohydrate binding domains that facilitate the strong binding of the GH catalytic modules with their dedicated, insoluble substrates. Examples of proteins having CMB6s belonging to this family are Microbispora bispora GghA, a 1,4-beta-D-glucan glucohydrolase (GH3); Clostridium thermocellum xylanase U (GH11), and Penicillium purpurogenum ABF3, a bifunctional alpha-L-arabinofuranosidase/xylobiohydrolase (GH43). GH3 comprises enzymes with activities including beta-glucosidase (hydrolyzes beta-galactosidase) and beta-xylosidase (hydrolyzes 1,4-beta-D-xylosidase). GH11 family comprises enzymes with xylanase (endo-1,4-beta-xylanase) activity which catalyze the hydrolysis of beta-1,4 bonds of xylan, the major component of hemicelluloses, to generate xylooligosaccharides and xylose. GH43 includes beta-xylosidases and beta-xylanases, using aryl-glycosides as substrates. CBM6 is an unusual CBM as it represents a chimera of two distinct binding sites with different modes of binding: binding site I within the loop regions and binding site II on the concave face of the beta-sandwich fold.
Glycosyl-hydrolase family 116, catalytic region. This represents a family of archaeal, bacterial and eukaryotic glycosyl hydrolases, that belong to superfamily GH116. The primary catabolic pathway for glucosylceramide is catalysis by the lysosomal enzyme glucocerebrosidase. In higher eukaryotes, glucosylceramide is the precursor of glycosphingolipids, a complex group of ubiquitous membrane lipids. Mutations in the human protein cause motor-neurone defects in hereditary spastic paraplegia. The catalytic nucleophile, identified in UniProtKB:Q97YG8_SULSO, is a glutamine-335, with the likely acid/base at Asp-442 and the aspartates at Asp-406 and Asp-458 residues also playing a role in the catalysis of glucosides and xylosides that are beta-bound to hydrophobic groups. The family is defined as GH116, which presently includes enzymes with beta-glucosidase, EC:3.2.1.21, beta-xylosidase, EC:3.2.1.37, and glucocerebrosidase EC:3.2.1.45 activity.