Hydrolysis of terminal non-reducing beta-D-galactose residues in beta-D-galactosides. Inhibited by Cu(2+) and Fe(2+), and moderately activated by divalent cations such as Co(2+), Mn(2+) and Zn(2+). Considerably activated by dithiothreitol, beta-mercaptoethanol and cysteine. Optimum pH is 6.5. No activity is detected at pH below 4.5. Optimum temperature is 70 degrees Celsius. It retains more than 75% of activity after incubation at 85 degrees Celsius and the half-life at 90 degrees Celsius is 1 hour. Thermostable. Homotrimer. The trimeric structure is essential to exhibit high enzymatic activity. Belongs to the glycosyl hydrolase 42 family.