Glycosyl hydrolase family 43 protein such as Clostridium thermocellum exo-beta-1,3-galactanase CtGH43 and Ruminococcus champanellensis arabinanase Ara43A
This glycosyl hydrolase family 43 (GH43) subgroup includes characterized enzymes with exo-beta-1,3-galactanase (EC 18.104.22.168, also known as galactan 1,3-beta-galactosidase) activity such as Clostridium thermocellum (Ct1,3Gal43A or CtGH43) and Phanerochaete chrysosporium 1,3Gal43A (Pc1, 3Gal43A), and arabinanase (EC 22.214.171.124) activity such as Ruminococcus champanellensis Ara43A. 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.
Comment:Three active site residues of the beta-propeller architecture of glycoside hydrolase families GH32, GH43, GH62 and GH68; in galactan beta-1,3-galactosidases (EC 126.96.36.199) the first of these residue is a Gly