Amylases, also known as diastases, are a group of enzymes that break down starch or glycogen variously to dextrin, maltose (a disaccharide), and glucose (a monosaccharide). In animals, amylases are secreted by the salivary glands (salivary amylase) and the pancreas (pancreatic amylase) and aid in digestion. They are also secreted by plants and microorganisms.
An amylase test may be carried out on someone if it's suspected there may be a blockage in the duct that carries digestive enzymes to the small intestine. This may be due to pancreatic cancer, gallstones, or a narrowing of the duct or the sphincter that separates the pancreatic duct from the bowel.