Senescence-associated beta-galactosidase (SA-β-gal or SABG) is a hypothetical hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides.
[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.
[4][5][6] Today this phenomenon is explained by the overexpression and accumulation of the endogenous lysosomal beta-galactosidase specifically in senescent cells.
[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.