Glycosyl hydrolase family 43 protein such as Clostridium thermocellum exo-beta-1,3-galactanase (Ct1,3Gal43A or CtGH43)
This glycosyl hydrolase family 43 (GH43) subgroup includes characterized enzymes with exo-beta-1,3-galactanase (EC 3.2.1.145, also known as galactan 1,3-beta-galactosidase) activity such as Clostridium thermocellum exo-beta-1,3-galactanase (Ct1,3Gal43A or CtGH43), Streptomyces avermitilis MA-4680 = NBRC 14893 (Sa1,3Gal43A;SAV2109) (1,3Gal43A), and Ruminiclostridium thermocellum ATCC 27405 (Ct1,3Gal43A;CtGH43;Cthe_0661) (1,3Gal43A). It belongs to the GH43_CtGH43 subgroup of the glycosyl hydrolase clan F (according to carbohydrate-active enzymes database (CAZY)) which includes family 43 (GH43) and 62 (GH62) families. GH43_CtGH43 includes proteins such as Clostridium thermocellum exo-beta-1,3-galactanase (Ct1,3Gal43A or CtGH43) which is comprised of the GH43 domain, a CBM13 domain, and a dockerin domain, exhibits an unusual ability to hydrolyze beta-1,3-galactan in the presence of a beta-1,6 linked branch, and is missing an essential acidic residue suggesting a mechanism by which it bypasses beta-1,6 linked branches in the substrate. 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.
Feature 1: active site [active site], 3 residue positions
Conserved feature residue pattern:G [DEN] [DEN]
Evidence:
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 3.2.1.145) the first of these residue is a Gly
Jiyao W et al.(2023). "The conserved domain database in 2023.",