β-galactosidase is a hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides. Substrates of different β-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins.http://www.creative-enzymes.com/product/-Galactosidase-42A-From-Bifidobacterium-Longum-Recombinant_3595.html