Broad specificity glycosidase of the intestinal brush border membrane that hydrolyzes lactose, the main sugar in mammalian milk, to produce D-glucose and D-galactose (PubMed:3929764, PubMed:9762914, PubMed:12594539, PubMed:16400612). The mature protein is composed of two domains that catalyze the hydrolysis of beta-glucopyranosides and beta-galactopyranosides, with a preference for hydrophilic aglycones (in lactose and cellobiose) for one domain and hydrophobic aglycones (in phlorizin and glycosylceramides) for the other (PubMed:3929764, PubMed:9762914, PubMed:12594539). H2O + lactose = beta-D-galactose + D-glucose H2O + phlorizin = beta-D-glucose + phloretin D-cellobiose + H2O = beta-D-glucose + D-glucose H2O + quercetin 4'-O-beta-D-glucoside = beta-D-glucose + quercetin H2O + quercetin 3-O-beta-D-glucoside = beta-D-glucose + quercetin H2O + kaempferol 3-O-beta-D-glucoside = beta-D-glucose + kaempferol H2O + luteolin 7-O-beta-D-glucoside = beta-D-glucose + luteolin H2O + luteolin 4'-O-beta-D-glucoside = beta-D-glucose + luteolin (2S)-naringenin 7-O-beta-D-glucoside + H2O = (2S)-naringenin + beta-D-glucose eriodictyol-7-O-beta-D-glucoside + H2O = (S)-eriodictyol + beta-D-glucose apigenin 7-O-beta-D-glucoside + H2O = apigenin + beta-D-glucose daidzein 7-O-beta-D-glucoside + H2O = beta-D-glucose + daidzein + H(+) genistein 7-O-beta-D-glucoside + H2O = beta-D-glucose + genistein glycosyl-N-acylsphingosine + H2O = N-acylsphingosine + a sugar. beta-D-glucosyl-(1<->1')-N-hexadecanoylsphing-4-enine + H2O = beta-D-glucose + N-hexadecanoylsphing-4-enine beta-D-galactosyl-(1<->1')-N-hexadecanoylsphingosine + H2O = beta-D-galactose + N-hexadecanoylsphing-4-enine beta-D-galactosyl-(1<->1')-N-hexadecanoylsphinganine + H2O = beta-D-galactose + N-hexadecanoylsphinganine beta-D-glucosyl-(1<->1')-N-hexadecanoylsphinganine + H2O = beta-D-glucose + N-hexadecanoylsphinganine Homodimer. Brush border. Specifically expressed in small intestine. The glycosyl hydrolase-1 3/region III carries the phlorizin hydrolase/glycosylceramidase activities. The glycosyl hydrolase-1 4/region IV carries the lactase activity. N-glycosylated. The disease is caused by variants affecting the gene represented in this entry. Belongs to the glycosyl hydrolase 1 family. Lactase entry Darwin's dessert - Issue 111 of November 2009