The main function of beta galactosidase is to cleave lactose to form galactose and glucose, which subsequently enter glycolysis. A second function is to facilitate the formation of allolactose from lactose via transglycosylation. Its third main function is to break down the allolactose molecule into monosaccharides. This allows the cell to efficiently modulate the concentration of allolactose and alters its response to the availability of lactose.