Glycosyl hydrolase family 43 protein; uncharacterized. This glycosyl hydrolase family 43 (GH43)-like subfamily includes uncharacterized enzymes similar to those with beta-1,4-xylosidase (xylan 1,4-beta-xylosidase; EC 3.2.1.37), beta-1,3-xylosidase (EC 3.2.1.-), alpha-L-arabinofuranosidase (EC 3.2.1.55), arabinanase (EC 3.2.1.99), xylanase (EC 3.2.1.8), endo-alpha-L-arabinanase and galactan 1,3-beta-galactosidase (EC 3.2.1.145) 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. Many of the enzymes in this family 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.

Glycosyl hydrolase families 43 and 62 form CAZY clan GH-F. This glycosyl hydrolase clan F (according to carbohydrate-active enzymes database (CAZY)) includes family 43 (GH43) and 62 (GH62). GH43 includes enzymes with beta-xylosidase (EC 3.2.1.37), beta-1,3-xylosidase (EC 3.2.1.-), alpha-L-arabinofuranosidase (EC 3.2.1.55), arabinanase (EC 3.2.1.99), xylanase (EC 3.2.1.8), endo-alpha-L-arabinanases (beta-xylanases) and galactan 1,3-beta-galactosidase (EC 3.2.1.145) activities. GH62 includes enzymes characterized as arabinofuranosidases (alpha-L-arabinofuranosidases; EC 3.2.1.55) that specifically cleave either alpha-1,2 or alpha-1,3-L-arabinofuranose side chains from xylans. 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 of the enzymes in this family display both alpha-L-arabinofuranosidase and beta-D-xylosidase activity using aryl-glycosides as substrates. GH62 are also predicted to be inverting enzymes. A common structural feature of both, GH43 and GH62 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.

F5/8 type C domain. This domain is also known as the discoidin (DS) domain family.

Glycosyl hydrolase family 43 protein most having a F5/8 type C domain C-terminal to the GH43 domain. This glycosyl hydrolase family 43 (GH43) subgroup includes enzymes that have been annotated as having beta-xylosidase (EC 3.2.1.37), xylanase (EC 3.2.1.8), and beta-galactosidase (EC 3.2.1.145) activities, and some as F5/8 type C domain (also known as the discoidin (DS) domain)-containing proteins. Most contain a F5/8 type C domain C-terminal to the GH43 domain. It belongs to the glycosyl hydrolase clan F (according to carbohydrate-active enzymes database (CAZY)) which includes family 43 (GH43) and 62 (GH62) families. 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. Characterized enzymes belonging to this subgroup include Lactobacillus brevis (LbAraf43) and Weissella sp (WAraf43) which show activity with similar catalytic efficiency on 1,5-alpha-L-arabinooligosaccharides with a degree of polymerization (DP) of 2-3; size is limited by an extended loop at the entrance to the active site. 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 a thermostable family-43 glycoside hydrolase [Halothermothrix orenii H 168],4QQS_B Crystal structure of a thermostable family-43 glycoside hydrolase [Halothermothrix orenii H 168]