Description_x000D_ General description_x000D_ β-Galactosidase is a tetramer consisting of four equal subunits of 135,000 Da each. It is a sulfhydryl containing enzyme, with 19 cysteine residues per subunit._x000D_ Application_x000D_ β-Galactosidase is conjugated to an antibody that specifically recognizes a target molecule (enzyme immunoassay or EIA). β-Galactosidase is also used as a reporter enzyme to monitor the level of gene expression of a promoter._x000D_ Packaging_x000D_ 1000, 5000 units in glass bottle_x000D_ 10000 units in poly bottle_x000D_ Biochem/physiol Actions_x000D_ β-galactosidase cleaves lactose into its monosaccharide components, glucose and galactose. It also catalyses the transglycosylation of glucose into allolactose, the inducer of β-galactosidase, in a feedback loop._x000D_ β-galactosidase cleaves lactose into its monosaccharide components, glucose and galactose. It also catalyses the transglycosylation of glucose into allolactose, the inducer of β-galactosidase, in a feedback loop._x000D_ Physical properties_x000D_ Tetramer molecular weight 465 kDa (subunits 116.3 kDa each)_x000D_ Unit Definition_x000D_ One unit will hydrolyze 1.0 μmole of o-nitrophenyl β-D-galactoside to o-nitrophenol and D-galactose per min at pH 7.3 at 37 °C._x000D_ Physical form_x000D_ Partially purified; contains Tris buffer salts, magnesium chloride, DL-dithiothreitol and 2-mercaptoethanol