galactosidase, beta 1 | |||||||
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Identifiers | |||||||
Symbol | GLB1 | ||||||
Alt. symbols | SA-β-Gal | ||||||
NCBI gene | 2720 | ||||||
HGNC | 4298 | ||||||
OMIM | 611458 | ||||||
RefSeq | NM_000404 | ||||||
UniProt | P16278 | ||||||
Other data | |||||||
EC number | 3.2.1.23 | ||||||
Locus | Chr. 3 p22.3 | ||||||
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Senescence-associated beta-galactosidase (SA-β-gal or SABG) is a hypothetical hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides only in senescent cells. Senescence-associated beta-galactosidase, along with p16Ink4A, 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. They proposed a cytochemical assay based on production of a blue-dyed precipitate that results from the cleavage of the chromogenic substrate X-Gal, which stains blue when cleaved by galactosidase. Since then, even more specific quantitative assays were developed for its detection at pH 6.0.[4][5][6]
Today this phenomenon is explained by the overexpression and accumulation of the endogenous lysosomal beta-galactosidase specifically in senescent cells.[7] Its expression is not required for senescence.[7] However, it remains as the most widely used biomarker for senescent and aging cells, because it is easy to detect and reliable both in situ and in vitro.