A diastase (/ˈdaɪəsteɪz/; from Greek διαστασις, "separation") is any one of a group of enzymes which catalyses the breakdown of starch into maltose. Alpha amylase degrades starch to a mixture of the disaccharide maltose, the trisaccharide maltotriose, which contains three α (1-4)-linked glucose residues, and oligosaccharides known as dextrins that contain the α (1-6)-linked glucose branches. The commonly used -ase suffix for naming enzymes was derived from the name diastase. When used as a pharmaceutical drug, diastase has the ATC code A09AA01 (WHO).