| Background |
β-galactosidase (also known as β-gal) is an essential hydrolase enzyme that catalyzes the hydrolysis of galactose-containing carbohydrates into monosaccharides. Substrates of β-galactosides include lactose, various glycoproteins, ganglioside GM1, and lactosylceramides. β-galactosidase is used widely in molecular biology; for example, isolation of recombinant bacteria during molecular cloning utilizes α-complementation of the bacterial β-galactosidase gene (lacZ) in the presence of a β-gal substrate to identify recombinant clones. In cell biology, Senescence-Associated beta-galactosidase (SA-β-gal), defined as β-gal activity at pH 6.0, is a widely used marker of replicative senescence. While initially thought to derive from a unique isoform of β-galactosidase expressed specifically in senescent cells, SA-β-gal activity was subsequently shown to result from overexpression and accumulation of β-galactosidase in endogenous lysosomes, and is not specifically required for replicative senescence.
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