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Key Documents

G6008

Sigma-Aldrich

β-Galactosidase from Escherichia coli

Grade VI, lyophilized powder, ≥250 units/mg protein

Synonym(s):

β-D-Galactoside galactohydrolase, Lactase

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About This Item

CAS Number:
Enzyme Commission number:
EC Number:
MDL number:
UNSPSC Code:
12352204
NACRES:
NA.54

biological source

Escherichia coli

Quality Level

type

Grade VI

form

lyophilized powder

specific activity

≥250 units/mg protein

mol wt

465 kDa

does not contain

BSA as extender

composition

Protein, ≥50% biuret

shipped in

wet ice

storage temp.

−20°C

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General description

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.

Application

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.

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.
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

Partially purified; contains Tris buffer salts, magnesium chloride, DL-dithiothreitol and 2-mercaptoethanol

Storage Class

11 - Combustible Solids

wgk_germany

WGK 3

flash_point_f

Not applicable

flash_point_c

Not applicable

ppe

Eyeshields, Gloves, type N95 (US)


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David P Klebl et al.
Frontiers in molecular biosciences, 9, 945772-945772 (2022-08-23)
Advances in single particle cryo-EM data collection and processing have seen a significant rise in its use. However, the influences of the environment generated through grid preparation, by for example interactions of proteins with the air-water interface are poorly understood
PURIFICATION, COMPOSITION, AND MOLECULAR WEIGHT OF THE BETA-GALACTOSIDASE OF ESCHERICHIA COLI K12.
G R CRAVEN et al.
The Journal of biological chemistry, 240, 2468-2477 (1965-06-01)
D C Young et al.
Analytical biochemistry, 215(1), 24-30 (1993-11-15)
Bacterial beta-galactosidase is one of several reporter enzymes used in studying the transcriptional activity of eukaryotic promoters. Although it is one of the easiest and least expensive enzymes to assay, its use has been limited because of its low sensitivity
K Kato et al.
Journal of immunology (Baltimore, Md. : 1950), 116(6), 1554-1560 (1976-06-01)
1. A method for the conjugation of the Fab' fragment of rabbit IgG with beta-D-galactosidase from Escherichia coli is described. The method consists of two main steps: treatment of the Fab' fragments containing sulfhydryl groups with excess N,N'-o-phenylenedimaleimide, to introduce
D H Juers et al.
Protein science : a publication of the Protein Society, 8(1), 122-136 (1999-04-21)
Beta-galactosidase (lacZ) from Escherichia coli is a 464 kDa homotetramer. Each subunit consists of five domains, the third being an alpha/beta barrel that contains most of the active site residues. A comparison is made between each of the domains and

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