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Detecting senescence cells can be achieved by measuring the lysosomal Beta-Galactosidase activity. [19] A new isoform for beta-galactosidase with optimum activity at pH 6.0 (Senescence Associated beta-gal or SA-beta-gal) [20] which is specifically expressed in senescence (the irreversible growth arrest of cells). Specific quantitative assays ...
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.
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 ...
When the target gene is not found in the vector, the alpha fragment gene would be active, producing the alpha fragment and allowing for B-galactosidase to gain its activity. To trace the activity of B-galactosidase a colorless analog of lactose is used, X-gal. The hydrolysis of X-gal by B-galactosidase produces galactose, a blue colored compound.
This process is analogous to hydrolysis of X-gal by Beta-galactosidase [5] to produce blue cells as is commonly practiced in bacterial reporter gene assays. For other types of detection, common substrates are p-nitrophenyl β-D-glucuronide for the spectrophotometric assay and 4-methylumbelliferyl-beta-D-glucuronide (MUG) for the fluorimetric ...
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-nitrophenol.
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 ...
Reporter genes can be used to assay for the activity of a particular promoter in a cell or organism. [23] In this case there is no separate "gene of interest"; the reporter gene is simply placed under the control of the target promoter and the reporter gene product's activity is quantitatively measured.