A diastase (//; from Greek διάστασις, "separation") is any one of a group of enzymes that 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" refers to any α-, β-, or γ-amylase (all of which are hydrolases) that can break down carbohydrates.
Amylases can also be extracted from other sources including plants, saliva and milk.
Urine diastase is useful in diagnosing uncertain abdominal cases (especially when pancreatitis is suspected), stones in the common bile duct (choledocholithiasis), jaundice and in ruling out post-operative injury to the pancreas; provided that the diastase level is correlated with clinical features of the patient.
Diastase is also used in conjunction with periodic acid–Schiff stain in histology. For example, glycogen is darkly stained by PAS but can be dissolved by diastase. Fungi, on the other hand, stains darkly with PAS even after treatment by diastase.
- Gray, G.M. (1975). "Carbohydrate digestion and absorption". New England Journal of Medicine. 292 (23): 1225–1230. doi:10.1056/NEJM197506052922308. PMID 1093023.
- Hill, Robert; Needham, Joseph (1970). The Chemistry of Life: Eight Lectures on the History of Biochemistry. London: Cambridge University Press. p. 17.
- Silverman, Richard B. (2002). The Organic Chemistry of Enzyme-catalyzed Reactions (2nd ed.). London: Academic Press. p. 1.
- Stenesh, Jochanan (1998). Biochemistry. 2. New York: Plenum. p. 83.
- Meyers, Robert A., ed. (1995). Molecular Biology and Biotechnology: A Comprehensive Desk Reference. New York: Wiley-VCH. p. 296.
- Payen & Persoz (1833), page 77. Payen and Persoz found diastase in the seeds of barley, oats, and wheat, as well as in potatoes (Payen & Persoz (1833), page 76).
- Payen & Persoz (1833), pages 75-76.
- Etymology of "diastase"
- Oliver, Garrett (2011). The Oxford Companion to Beer. Oxford: Oxford University Press. p. 49. ISBN 0199912106. Retrieved 2013-12-27.
Most of the activity of diastase can be attributed to the activities of two enzymes, alpha and beta amylase, and, to a lesser extent, gamma amylase (together, the amylases), although many other enzymes are also present.
- 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.
- Foged, Jens (March 1935). "The diagnostic value of urine diastase". The American Journal of Surgery. 27 (3): 439–446. doi:10.1016/S0002-9610(35)91022-4.
- Payen, A. et J.-F. Persoz (1833) "Mémoire sur la diastase, les principaux produits de ses réactions et leurs applications aux arts industriels" (Memoir on diastase, the principal products of its reactions, and their applications to the industrial arts), Annales de chimie et de physique, 2nd series, 53 : 73–92.