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β-Galactosidase (EC 3.2.1.23, beta-gal or β-gal; systematic name β-D-galactoside galactohydrolase) is a glycoside hydrolase enzyme that catalyzes hydrolysis of terminal non-reducing β-D-galactose residues in β-D-galactosides. (This enzyme digests many β-Galactosides, not just lactose.
The presence of an active β-galactosidase can be detected by X-gal, a colourless analog of lactose that may be cleaved by β-galactosidase to form 5-bromo-4-chloro-indoxyl, which then spontaneously dimerizes and oxidizes to form a bright blue insoluble pigment 5,5'-dibromo-4,4'-dichloro-indigo. This results in a characteristic blue colour in ...
The RNA transcript of the GLB1 gene is alternatively spliced and produces 2 mRNAs. The 2.5-kilobase transcript encodes the beta-galactosidase enzyme of 677 amino acids.The alternative 2.0-kb mRNA encodes a beta-galactosidase-related protein (S-Gal) that is only 546 amino acids long and that has no enzymatic activity.
The galactosidases are categorized as either alpha or beta, according to the category of glycoside they hydrolyze. The enzyme corresponding to an alpha-galactoside is called alpha-galactosidase ; it catalyzes the hydrolysis of substrates that contain α-galactosidic residues , such as glycosphingolipids or glycoproteins . [ 1 ]
ortho-Nitrophenyl-β-galactoside (ONPG) is a colorimetric and spectrophotometric substrate for detection of β-galactosidase activity. [1] This compound is normally colorless. However, if β-galactosidase is present, it hydrolyzes the ONPG molecule into galactose and ortho-nitrophen
Senescence-associated beta-galactosidase, along with p16 Ink4A, is regarded to be a biomarker of cellular senescence. [ 1 ] [ 2 ] Its existence was proposed in 1995 by Dimri et al. [ 3 ] following the observation that when beta-galactosidase assays were carried out at pH 6.0, only cells in senescence state develop staining.
X-gal itself is colorless, so the presence of blue-colored product may therefore be used as a test for the presence of active β-galactosidase. This also allows for bacterial β-galactosidase (so called lacZ ) to be used as a reporter in various applications. [5] Similarly, Xαgal is used as a reporter compound for α-galactosidase (e.g. Mel1 ...
A common reporter in bacteria is the E. coli lacZ gene, which encodes the protein beta-galactosidase. [10] This enzyme causes bacteria expressing the gene to appear blue when grown on a medium that contains the substrate analog X-gal.