amylase


amylase
/am"euh lays', -layz'/, n. Biochem.
1. any of a widely distributed class of enzymes that catalyze the hydrolysis of starch, glycogen, and related polysaccharides to oligosaccharides, maltose, or glucose.
2. any of several digestive enzymes that break down starches.
[1890-95; AMYL- + -ASE]

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      any member of a class of enzymes that catalyze the hydrolysis (splitting of a compound by addition of a water molecule) of starch into smaller carbohydrate molecules such as maltose (a molecule composed of two glucose molecules). Two categories of amylases, denoted alpha and beta, differ in the way they attack the bonds of the starch molecules.

      Alpha-amylase is widespread among living organisms. In the digestive systems of humans and many other mammals, an alpha-amylase called ptyalin is produced by the salivary glands, whereas pancreatic amylase is secreted by the pancreas into the small intestine.

      Ptyalin is mixed with food in the mouth, where it acts upon starches (starch). Although the food remains in the mouth for only a short time, the action of ptyalin continues for up to several hours in the stomach—until the food is mixed with the stomach secretions, the high acidity of which inactivates ptyalin. Ptyalin's digestive action depends upon how much acid is in the stomach, how rapidly the stomach contents empty, and how thoroughly the food has mixed with the acid. Under optimal conditions as much as 30 to 40 percent of ingested starches can be broken down to maltose by ptyalin during digestion in the stomach.

      When food passes to the small intestine, the remainder of the starch molecules are catalyzed mainly to maltose by pancreatic amylase. This step in starch digestion occurs in the first section of the small intestine (the duodenum), the region into which the pancreatic juices empty. The by-products of amylase hydrolysis are ultimately broken down by other enzymes into molecules of glucose, which are rapidly absorbed through the intestinal wall.

      Beta-amylases are present in yeasts, molds, bacteria, and plants, particularly in the seeds. They are the principal components of a mixture called diastase that is used in the removal of starchy sizing agents from textiles and in the conversion of cereal grains to fermentable sugars.

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Universalium. 2010.

Look at other dictionaries:

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  • amylase — [ amilaz ] n. f. • 1875; du lat. amylum et ase ♦ Chim., biol. Enzyme provoquant l hydrolyse de l amidon en maltose, puis en glucose, que l on rencontre dans la salive, le suc pancréatique, et dans divers micro organismes et végétaux. ⇒ diastase.… …   Encyclopédie Universelle

  • amylase — (n.) enzyme which brings about the hydrolysis of starch, 1893, from AMYL (Cf. amyl) + chemical suffix ASE (Cf. ase) …   Etymology dictionary

  • amylase — [am′ə lās΄] n. [ AMYL(O) + ASE] an enzyme that helps change starch into sugar: it is found in saliva, pancreatic juice, etc.: see also DIASTASE, AMYLOPSIN …   English World dictionary

  • Amylase — Amylasen sind Enzyme, die bei den meisten Lebewesen vorkommen, und die Polysaccharide abbauen. Heutzutage wird α Amylase auch gentechnisch hergestellt. [1] Ihre Wirkung besteht darin, dass sie Polysaccharide (z. B. Stärke) an den… …   Deutsch Wikipedia

  • Amylase — L amylase (EC 3.2.1.1) est une enzyme digestive classée comme saccharidase (enzyme qui brise les polysaccharides). C est surtout un constituant du suc pancréatique et de la salive, requis pour le catabolisme des glucides à longue chaîne (comme l… …   Wikipédia en Français

  • Amylase — Amy|la|se 〈f. 19; Chem.〉 Enzym, das Stärke zu Maltose (Malzzucker) abbaut; Sy Diastase * * * A|my|la|se [von Amyl (2) u. ↑ ase], die; , n; Syn.: Diastase: Stärke (vgl. Amylose u. Amylopektin), Glykogen u. a. Glucane selektiv spaltende ↑… …   Universal-Lexikon

  • amylase — /ˈæməleɪz/ (say amuhlayz) noun any of several enzymes, occurring in digestive juices, saliva, and plants which hydrolyse starches to glucose and maltose; the main types are alpha amylase and beta amylase. {amyl + ase} …   Australian English dictionary

  • amylase — One of a group of amylolytic enzymes that cleave starch, glycogen, and related 1,4 α glucans. * * * am·y·lase am ə .lās, .lāz n any of a group of enzymes (as amylopsin) that catalyze the hydrolysis of starch and glycogen or their intermediate… …   Medical dictionary

  • amylase —    An enzyme found in plant and animal tissue which promotes the conversion of starch and glycogen into maltose. In forensics, the Phadebas test is used to detect the enzyme amylase which found in saliva …   Forensic science glossary


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