Glycosyl hydrolase family 43 protein such as Aspergillus niger DMS1957 xylanase D (XlnD); includes mostly xylanases
This glycosyl hydrolase family 43 (GH43) subgroup includes enzymes that have mostly been annotated as xylanases (endo-alpha-L-arabinanase, EC 3.2.1.8). It belongs to the GH43_bXyl-like subgroup of the glycosyl hydrolase clan F (according to carbohydrate-active enzymes database (CAZY)) which includes family 43 (GH43) and 62 (GH62) families. The GH43_bXyl-like subgroup includes enzymes that have been annotated as xylan-digesting beta-xylosidases (EC 3.2.1.37) and xylanases, as well the Bacteroides thetaiotaomicron VPI-5482 alpha-L-arabinofuranosidases (EC 3.2.1.55) (BT3675;BT_3675) and (BT3662;BT_3662). 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.
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