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. Diastase was the first enzyme discovered. It was extracted from malt solution in 1833 by Anselme Payen and Jean-François Persoz, chemists at a French sugar factory. The name "diastase" comes from the Greek word διάστασις (diastasis) (a parting, a separation) because when beer mash is heated, the enzyme causes the starch in the barley seed to transform quickly into soluble sugars and hence the husk to separate from the rest of the seed. Today, diastase means any α-, β-, or γ-amylase (all of them hydrolases) that can break down carbohydrates.
The commonly used -ase suffix for naming enzymes was derived from the name diastase.
These days, diastase can be taken out from the barley seed even after all the beer ingredients were mixed and heated. This beneficial enzyme can also be extracted from various other sources. These include plants, saliva and milk. However, for obtaining a natural diastase numerous natural sources can be used.
^The naming of enzymes using the suffix "-ase" has been traced to French scientist Émile Duclaux (1840-1904), who intended to honor the discoverers of diastase by introducing the practice in his book Traité de Microbiologie, vol. 2 (Paris, France: Masson and Co., 1899), Chapter 1, especially page 9.