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G5635 Sigma-Aldrich

β-Galactosidase from Escherichia coli

Grade VIII, lyophilized powder, ≥500 units/mg protein

Synonym: β-D-Galactoside galactohydrolase, Lactase



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.


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.


1000, 3000, 5000, 15000 units in serum bottle

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 properties

Tetramer molecular weight 465 kDa (subunits 116.3 kDa each)

Unit Definition

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.

Physical form

Contains Tris buffer salts and magnesium chloride

Safety & Documentation

Safety Information

NONH for all modes of transport
WGK Germany 
Protocols & Articles


HPLC Analysis of Protein Standards (1) on BIOshell™ A400 Protein C4

From our library of Articles, Sigma-Aldrich presents HPLC Analysis of Protein Standards (1) on BIOshell™ A400 Protein C4
Keywords: Chromatography, High performance liquid chromatography, Reversed-phase chromatography

HPLC Analysis of Proteins on BIOshell™ A400 Protein C18

From our library of Articles, Sigma-Aldrich presents HPLC Analysis of Proteins on BIOshell™ A400 Protein C18
Keywords: High performance liquid chromatography

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Enzymes & Proteins

Application Index | Enzyme Index | Substrate Index | Inhibitor Index | Cofactor Index | Lectin Index
Keywords: Cell signaling, Diagnostic, Drug discovery, Metabolomics, Molecular biology

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