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]
It consists of three structural domains. The C-terminal domain forms a two layered jelly roll motif. This domain is situated at the base of the catalytic domain, however its function remains unknown.[8] The central domain is the catalytic domain, which binds a phosphate ion that is proximal the highly conserved Glu. The arrangement of the phosphate and the glutamate is thought to cause nucleophilic attack on the anomeric carbon atom.[8] The catalytic domain also forms the majority of the dimerisation interface. The N-terminal domain is believed to be essential for catalytic activity[8] although its precise function remains unknown.