Glycosyl hydrolase families: GH43, GH62, GH32, GH68, GH117, CH130. Members of the glycosyl hydrolase families 32, 43, 62, 68, 117 and 130 (GH32, GH43, GH62, GH68, GH117, GH130) all possess 5-bladed beta-propeller domains and comprise clans F and J, as classified by the carbohydrate-active enzymes database (CAZY). Clan F consists of families GH43 and GH62. GH43 includes beta-xylosidases (EC 3.2.1.37), beta-xylanases (EC 3.2.1.8), alpha-L-arabinases (EC 3.2.1.99), and alpha-L-arabinofuranosidases (EC 3.2.1.55), using aryl-glycosides as substrates, while family GH62 contains alpha-L-arabinofuranosidases (EC 3.2.1.55) that specifically cleave either alpha-1,2 or alpha-1,3-L-arabinofuranose sidechains from xylans. These are inverting enzymes (i.e. they invert the stereochemistry of the anomeric carbon atom of the substrate) that have an aspartate as the catalytic general base, a glutamate as the catalytic general acid and another aspartate that is responsible for pKa modulation and orienting the catalytic acid. Clan J consists of families GH32 and GH68. GH32 comprises sucrose-6-phosphate hydrolases, invertases (EC 3.2.1.26), inulinases (EC 3.2.1.7), levanases (EC 3.2.1.65), eukaryotic fructosyltransferases, and bacterial fructanotransferases while GH68 consists of frucosyltransferases (FTFs) that include levansucrase (EC 2.4.1.10); beta-fructofuranosidase (EC 3.2.1.26); inulosucrase (EC 2.4.1.9), while GH68 consists of frucosyltransferases (FTFs) that include levansucrase (EC 2.4.1.10); beta-fructofuranosidase (EC 3.2.1.26); inulosucrase (EC 2.4.1.9), all of which use sucrose as their preferential donor substrate. Members of this clan are retaining enzymes (i.e. they retain the configuration at anomeric carbon atom of the substrate) that catalyze hydrolysis in two steps involving a covalent glycosyl enzyme intermediate: an aspartate located close to the N-terminus acts as the catalytic nucleophile and a glutamate acts as the general acid/base; a conserved aspartate residue in the Arg-Asp-Pro (RDP) motif stabilizes the transition state. Structures of all families in the two clans manifest a funnel-shaped active site that comprises two subsites with a single route for access by ligands. Also included in this superfamily are GH117 enzymes that have exo-alpha-1,3-(3,6-anhydro)-l-galactosidase activity, removing terminal non-reducing alpha-1,3-linked 3,6-anhydro-l-galactose residues from their neoagarose substrate, and GH130 that are phosphorylases and hydrolases for beta-mannosides, involved in the bacterial utilization of mannans or N-linked glycans.

Glycosyl hydrolase families: GH43, GH62, GH32, GH68, GH117, CH130. Members of the glycosyl hydrolase families 32, 43, 62, 68, 117 and 130 (GH32, GH43, GH62, GH68, GH117, GH130) all possess 5-bladed beta-propeller domains and comprise clans F and J, as classified by the carbohydrate-active enzymes database (CAZY). Clan F consists of families GH43 and GH62. GH43 includes beta-xylosidases (EC 3.2.1.37), beta-xylanases (EC 3.2.1.8), alpha-L-arabinases (EC 3.2.1.99), and alpha-L-arabinofuranosidases (EC 3.2.1.55), using aryl-glycosides as substrates, while family GH62 contains alpha-L-arabinofuranosidases (EC 3.2.1.55) that specifically cleave either alpha-1,2 or alpha-1,3-L-arabinofuranose sidechains from xylans. These are inverting enzymes (i.e. they invert the stereochemistry of the anomeric carbon atom of the substrate) that have an aspartate as the catalytic general base, a glutamate as the catalytic general acid and another aspartate that is responsible for pKa modulation and orienting the catalytic acid. Clan J consists of families GH32 and GH68. GH32 comprises sucrose-6-phosphate hydrolases, invertases (EC 3.2.1.26), inulinases (EC 3.2.1.7), levanases (EC 3.2.1.65), eukaryotic fructosyltransferases, and bacterial fructanotransferases while GH68 consists of frucosyltransferases (FTFs) that include levansucrase (EC 2.4.1.10); beta-fructofuranosidase (EC 3.2.1.26); inulosucrase (EC 2.4.1.9), while GH68 consists of frucosyltransferases (FTFs) that include levansucrase (EC 2.4.1.10); beta-fructofuranosidase (EC 3.2.1.26); inulosucrase (EC 2.4.1.9), all of which use sucrose as their preferential donor substrate. Members of this clan are retaining enzymes (i.e. they retain the configuration at anomeric carbon atom of the substrate) that catalyze hydrolysis in two steps involving a covalent glycosyl enzyme intermediate: an aspartate located close to the N-terminus acts as the catalytic nucleophile and a glutamate acts as the general acid/base; a conserved aspartate residue in the Arg-Asp-Pro (RDP) motif stabilizes the transition state. Structures of all families in the two clans manifest a funnel-shaped active site that comprises two subsites with a single route for access by ligands. Also included in this superfamily are GH117 enzymes that have exo-alpha-1,3-(3,6-anhydro)-l-galactosidase activity, removing terminal non-reducing alpha-1,3-linked 3,6-anhydro-l-galactose residues from their neoagarose substrate, and GH130 that are phosphorylases and hydrolases for beta-mannosides, involved in the bacterial utilization of mannans or N-linked glycans.

Glycosyl hydrolase family 117 (GH117). This glycoside hydrolase 117 (GH117) family includes alpha-1,3-L-neoagarooligosaccharide hydrolase (EC 3.2.1.-); alpha-1,3-L-neoagarobiase/neoagarobiose hydrolase (NABH, EC 3.2.1.-). In the agarolytic pathway, in order to metabolize agar, NABH is an essential enzyme because it converts alpha-neoagarobiose (O-3,6-anhydro-alpha-l-galactopyranosyl-(1,3)-d-galactose) into fermentable monosaccharides (d-galactose and 3,6-anhydro-l-galactose). Thus, these enzymes have exo-alpha-1,3-(3,6-anhydro)-l-galactosidase activity, removing terminal non-reducing alpha-1,3-linked 3,6-anhydro-l-galactose residues from their neoagarose substrate. This family includes Zobellia galactanivorans enzymes, Zg4663 and Zg3615 (also known as ZgAhgA and ZgAhgB, respectively) that have been shown to have similar activity on unsubstituted agarose oligosaccharides while Zg3597 has been shown to be inactive, possibly due to differences in dimerization conformation, active-site structure and function. GH117 shares distant sequence similarity with families GH43 and GH32. A common structural feature of all these enzymes is a 5-bladed beta-propeller domain, similar to GH43, that contains the catalytic acid and catalytic base. A long V-shaped groove, partially enclosed at one end, forms a single extended substrate-binding surface across the face of the propeller.

Glycosyl hydrolase family 43 protein such as endo-alpha-L-arabinanase. This glycosyl hydrolase family 43 (GH43) subgroup includes mostly enzymes with alpha-L-arabinofuranosidase (ABF; EC 3.2.1.55) and endo-alpha-L-arabinanase (ABN; EC 3.2.1.99) activities. These are inverting enzymes (i.e. they invert the stereochemistry of the anomeric carbon atom of the substrate) that have an aspartate as the catalytic general base, a glutamate as the catalytic general acid and another aspartate that is responsible for pKa modulation and orienting the catalytic acid. The GH43 ABN enzymes hydrolyze alpha-1,5-L-arabinofuranoside linkages while the ABF enzymes cleave arabinose side chains so that the combined actions of these two enzymes reduce arabinan to L-arabinose and/or arabinooligosaccharides. These arabinan-degrading enzymes are important in the food industry for efficient production of L-arabinose from agricultural waste; L-arabinose is often used as a bioactive sweetener. A common structural feature of GH43 enzymes is a 5-bladed beta-propeller domain that contains the catalytic acid and catalytic base. A long V-shaped groove, partially enclosed at one end, forms a single extended substrate-binding surface across the face of the propeller.

Glycosyl hydrolase family 43 protein such as Halothermothrix orenii H 168 alpha-L-arabinofuranosidase (HoAraf43;Hore_20580). This glycosyl hydrolase family 43 (GH43) subgroup includes Halothermothrix orenii H 168 alpha-L-arabinofuranosidase (EC 3.2.1.55) (HoAraf43;Hore_20580). It belongs to the glycosyl hydrolase clan F (according to carbohydrate-active enzymes database (CAZY)) which includes family 43 (GH43) and 62 (GH62) families. This GH43_ HoAraf43-like subgroup includes enzymes that have been annotated as having xylan-digesting beta-xylosidase (EC 3.2.1.37) and xylanase (endo-alpha-L-arabinanase, EC 3.2.1.8) activities. GH43 are inverting enzymes (i.e. they invert the stereochemistry of the anomeric carbon atom of the substrate) that have an aspartate as the catalytic general base, a glutamate as the catalytic general acid and another aspartate that is responsible for pKa modulation and orienting the catalytic acid. Many GH43 enzymes display both alpha-L-arabinofuranosidase and beta-D-xylosidase activity using aryl-glycosides as substrates. A common structural feature of GH43 enzymes is a 5-bladed beta-propeller domain that contains the catalytic acid and catalytic base. A long V-shaped groove, partially enclosed at one end, forms a single extended substrate-binding surface across the face of the propeller.

Crystalstructure of alpha-neoagarobiose hydrolase (ALPHA-NABH) from Saccharophagus degradans 2-40 [Saccharophagus degradans 2-40],3R4Y_B Crystal structure of alpha-neoagarobiose hydrolase (ALPHA-NABH) from Saccharophagus degradans 2-40 [Saccharophagus degradans 2-40],3R4Z_A Crystal structure of alpha-neoagarobiose hydrolase (ALPHA-NABH) in complex with alpha-d-galactopyranose from Saccharophagus degradans 2-40 [Saccharophagus degradans 2-40],3R4Z_B Crystal structure of alpha-neoagarobiose hydrolase (ALPHA-NABH) in complex with alpha-d-galactopyranose from Saccharophagus degradans 2-40 [Saccharophagus degradans 2-40]