Beta galactosidase is made to bind to galactose and glucose, which are the two monosaccharides of lactose. At the galactose subsite, this enzyme binds efficiently to d-galactose and is specific in recognizing this sugar. Some sugars with alterations at position 6 are able to bind, but are typically inefficient substrates. Even slight modifications at position 6 greatly reduce the efficiency of the enzyme in processing sugars. At the glucose subsite, beta galactosidase shows low specificity for d-glucose, allowing for the interchanging of different alcohols. This subsite is hydrophobic, and thus beta galactosidase with hydrophobic groups instead of glucose binds effectively. The affinity for d-glucose increases greatly after the glycosidic bond breaks.