Glycoside hydrolasesEC3.2.1. are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycoside hydrolases, based on sequence similarity, has led to the definition of >100 different families.[1][2][3] This classification is available on the CAZy web site,[4][5] and also discussed at CAZypedia, an online encyclopedia of carbohydrate active enzymes.[6][7]
Glycoside hydrolase family 43 CAZY GH_43 includes enzymes with the following activities, beta-xylosidase (EC3.2.1.37), alpha-L-arabinofuranosidase (EC3.2.1.55); arabinanase (EC3.2.1.99), and xylanase (EC3.2.1.8). The structure of arabinanase Arb43A from Cellvibrio japonicus reveals a five-bladed beta-propeller fold. A long V-shaped groove, partially enclosed at one end, forms a single extended substrate-binding surface across the face of the propeller.[8]