Senescence-associated beta-galactosidase

Senescence-associated beta-galactosidase (SA-β-gal or SABG) is a hypothetical hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides. Senescence-associated beta-galactosidase, along with p16^Ink4A, is regarded to be a biomarker of cellular senescence.^[1][2]

galactosidase, beta 1
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
Search for Structures Swiss-model Domains InterPro

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.^{[citation needed]}