Merck, G5635-15KU, β-Galactosidase from Escherichia coli

General description
β-Galactosidase is a tetramer consisting of four equal subunits of 135,000 each. It is a sulfhydryl containing enzyme, with 19 cysteine residues per subunit.
Tetramer molecular weight 465 kDa (subunits 116.3 kDa each)
Application
β-Galactosidase is conjugated to an antibody which 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. It may be used as a positive control protein with anti-β-galactosidase antibodies.
Biochem/physiol Actions
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.
Physical form
Contains Tris buffer salts and magnesium chloride
Other Notes
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.