O-Glycosyl hydrolases 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 glycosyl hydrolases, based on sequence similarity, has led to the definition of 85 different families. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site.Glycoside hydrolase 2 <db_xref db="CAZY" dbkey="GH2"/>comprises enzymes with several known activities; beta-galactosidase ; beta-mannosidase ; beta-glucuronidase .These enzymes contain a conserved glutamic acid residue which has been shown, in Escherichia coli lacZ , to be the general acid/base catalyst in the active site of the enzyme.