Involved in the hydrolysis of transgalactooligosaccharides (TOS). Highly active towards Gal(beta1-4)Gal and Gal(beta1-4)-Gal-containing oligosaccharides. Low activity towards Gal(beta1-3)Gal, lactose and Gal(beta1-3)GalOMe. No activity towards Gal(beta1-6)Gal, Gal(beta1-4)Man, Gal(alpha1-4)Gal, Gal(alpha1-3)Gal(beta1-4)Gal, lactulose, 3'fucosyllactose, lacto-N-fucopentaose I, lacto-N-fucopentaose II, cellobiose, maltose or sucrose. No transglycosylation activity is found at high substrate concentrations (100 mg/ml) and only low transglycosylation activity at lower substrate concentrations (10 mg/ml). Hydrolysis of terminal non-reducing beta-D-galactose residues in beta-D-galactosides. Inhibited by high substrate concentrations (100 mg/ml). No effect on activity with various EDTA concentrations (0-1 mM). 20-fold higher activity when cells grown on TOS than when cells grown on galactose, glucose and lactose. Optimum is pH 6.0 using PNPG or TOS as substrate. Not active below pH 5. Optimum temperature is 50 degrees Celsius using PNPG as substrate (PubMed:15480628). Optimum temperature is 35 degrees Celsius using TOS as substrate (PubMed:10742215). Stable at 40 degrees Celsius. Half-life time at 50 degrees Celsius is 10 minutes. Trimer (PubMed:15480628). Tetramer (PubMed:10742215). The N-terminus is blocked. Belongs to the glycosyl hydrolase 42 family. Extended N-terminus.