amylase
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amylase
Amylase
An enzyme which breaks down (hydrolyzes) starch, the reserve carbohydrate in plants, and glycogen, the reserve carbohydrate in animals, into reducing fermentable sugars, mainly maltose, and reducing nonfermentable or slowly fermentable dextrins. Amylases are classified as saccharifying (β-amylase) and as dextrinizing (α-amylases). The α- and β-amylases are specific for the α- and β-glucosidic bonds which connect the monosaccharide units into large aggregates, the polysaccharides. The α-amylases are found in all types of organs and tissues, whereas β-amylase is found almost exclusively in higher plants. See Carbohydrate, Enzyme, Glycogen, Maltose
In animals the highest concentrations of amylase are found in the saliva and in the pancreas. Salivary amylase is also known as ptyalin and is found in humans, the ape, pig, guinea pig, squirrel, mouse, and rat.
In plants, starch is broken down during the germination of seeds (rich in starch) by associated plant enzymes into sugars. These constitute the chief energy source in the early development of the plant. β-Amylase occurs abundantly in seeds and cereals such as malt. It also is found in yeasts, molds, and bacteria.
Amylase
any of the enzymes which catalyze the hydrolysis of starches, glycogen, and related polysaccharides by splitting the glucoside bonds between the first and fourth carbon atoms. Three types of amylase are differentiated: alpha-amylase, beta-amylase, and glucoamylase. Alpha-amylase is found in animals, plants, and microorganisms. Reactions in which it participates form mainly dextrins. Beta-amylase, typical in higher plants, catalyzes the formation of maltoses and macromolecular dextrins. Glucoamylase is found in the blood of animals, in fungi, in bacteria, and elsewhere. It catalyzes the formation of glucose and dextrins. Usually hydrolysis of polysaccharides occurs with the simultaneous participation of various amylases. Saccharification of starch by the action of an extract of germinated barley seeds (the fermentative action of amylases) was first described by the Russian academician, K. S. Kirkhgof in 1814. Diastase, the unpurified complex of amylases produced from a malt extract by the French scientists A. Payen and J. Persoz in 1833, was the first enzyme preparation. Some amylases have already been produced in crystalline form. Amylases are specific for various species of organisms. Their physiological role consists in the mobilization of polysaccharide reserves in the cells—for example, in seed germination. Their role in digestion is important; amylases are present in the saliva and in the pancreases of humans and of animals. Microorganisms use starch and excrete amylases into the atmosphere. Alpha-amylase, produced from molds and bacteria, is used for saccharification of starchy brewing mashes in the liquor industry and in breadmaking. Glucoamylase preparations are used to manufacture glucose from starch.
B. B. IURKEVICH