β-Galactosidase

β-Galactosidase is a glycoside hydrolase that hydrolyzes the β-glycosidic bond formed between galactose and its organic part. In Escherichia coli, the lacZ gene is the structural gene for β-galactosidase and can be used as part of the lac manipulator of the inducible system. β-Galactosidase hydrolyzes lactose to form glucose and galactose, which enter glycolysis, and also catalyzes the transgalactosylation of lactose to isolactose, which can be cleaved to monosaccharides.