Amylase is an enzyme which breaks down starch into sugars which the body can use.
More accurately, it is a family of similar enzymes which work in a wide range of animals, plants and fungi. There are two variants in humans: alpha-amylase, and gamma-amylase.
Alpha-amylase is a major digestive enzyme. Its optimum pH is 6.7–7.0. It is found in saliva and pancreatic juice. It takes starch chains and breaks them into smaller pieces with two or three glucose units. It can break down starch into maltose. It works in the mouth and stomach during digestion.
The gamma-amylase has most acidic optimum pH of all amylases because it is most active around pH 3. Therefore, it works best in the stomach, which does have an acidic pH.