The lactase enzyme is mainly known to interact with the lactose sugar which is a disaccharide. What the lactase does, like stated before, is breaks down the disaccharide lactose into 2 more simple monosaccharides called Glucose and Galactose. The lactose binds to the lactase to form an enzyme substrate complex, which consists of the Glucose and Galactose. The enzyme lactase is a catalyst, a compound that changes the speed of a chemical reaction without itself being changed by the reaction. Being an enzyme means that it is only speeding up a reaction that would already occur. The way this reaction would occur is the stomach acids having trouble breaking down the lactose, which would cause for all of the gas to build up in the stomach, allowing for diarrhea to occur. The good thing is that lactase being an enzyme means that the lactase molecules are recycled back into the system after they catalyze a certain something. The lactase enzyme can ONLY bind to lactase molecules because this is how their receptors are supposed to be. This is why the human body consists of so many different types of enzymes, for a number of different types of molecules, due to the fact that all of the amino acids make the enzymes differ from one another.