Dictionary:

amylase

  (ăm'ə-lās', -lāz')

Any of a group of enzymes that are present in saliva, pancreatic juice, and parts of plants and catalyze the hydrolysis of starch to sugar to produce carbohydrate derivatives.

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 also 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.

Enzymes that hydrolyse starch and glycogen. α-Amylase (dextrinogenic amylase or diastase) acts to produce small dextrin fragments from starch, while β-amylase (maltogenic amylase) liberates maltose, some free glucose, and isomaltose from the branch points in amylopectin.

Salivary amylase (sometimes called by its obsolete name of ptyalin) and pancreatic amylase are both α-amylases. See also Z-enzyme.

An enzymatic protein essential for changing starches into sugars.

An enzyme that catalyzes the hydrolysis of starch into simpler compounds. The α-amylases occur in animals and include pancreatic and salivary amylase; the β-amylases occur in higher plants. Measurement of serum α-amylase activity is an important diagnostic test for acute pancreatitis and acute attacks of chronic pancreatitis.

• a. isoenzymes — serum amylase is composed of a number of isoenzymes, isoamylases, probably originating from different tissues. Elevation of an isoenzyme of hepatic origin is found in hyperadrenocorticism.
• a. reaction — an identification test, based on an extracellular product of group A β-hemolytic streptococci.
• serum a. — the most significant laboratory aid in the diagnosis of acute pancreatitis or exacerbations of a chronic pancreatitis. Other organs may also produce the enzyme, or its isoenzymes, but the amounts are normally limited.
• urine a. — dogs excrete very little amylase in the urine in contrast to humans where urine levels of the enzyme may be valuable in assessing the progress of a case of pancreatitis.

Human salivary amylase. Calcium ion visible in pale khaki; chloride ion in green. From PDB 1SMD.

Human pancreatic amylase. Calcium ion visible in pale khaki; chloride ion in green. From PDB 1HNY.

Amylase is the name given to glycoside hydrolase enzymes that break down starch into glucose molecules. Amylase is also known as Ptyalin. Although the amylases are designated by different Greek letters, they all act on α-1,4-glycosidic bonds. Under the original name of diastase, amylase was the first enzyme to be found and isolated (by Anselme Payen in 1833).

Classification

α-Amylase

See main article at alpha-Amylase

(EC 3.2.1.1 ) (CAS# 9014-71-5) (alternate names: 1,4-α-D-glucan glucanohydrolase; glycogenase) The α-amylases are calcium metalloenzymes, completely unable to function in the absence of calcium. By acting at random locations along the starch chain, α-amylase breaks down long-chain carbohydrates, ultimately yielding maltotriose and maltose from amylose, or maltose, glucose and "limit dextrin" from amylopectin. Because it can act anywhere on the substrate, α-amylase tends to be faster acting than β-amylase. In animals, it is a major digestive enzyme.

In human physiology, both the salivary and pancreatic amylases are α-Amylases. They are discussed in much more detail at alpha-Amylase.

β-Amylase

(EC 3.2.1.2 ) (alternate names: 1,4-α-D-glucan maltohydrolase; glycogenase; saccharogen amylase) Another form of amylase, β-amylase is also synthesized by bacteria, fungi and plants. Working from the non-reducing end, β-amylase catalyzes the hydrolysis of the second α-1,4 glycosidic bond, cleaving off two glucose units (maltose) at a time. During the ripening of fruit, β-amylase breaks starch into sugar, resulting in the sweet flavor of ripe fruit. Both are present in seeds; β-amylase is present prior to germination whereas α-amylase and proteases appear once germination has begun. Cereal grain amylase is key to the production of malt. Many microbes also produce amylase to degrade extracellular starches. Animal tissues do not contain β-amylase, although it may be present in microrganisms contained within the digestive tract.

γ-Amylase

(EC 3.2.1.3 ) (alternative names: Glucan 1,4-α-glucosidase; amyloglucosidase; Exo-1,4-α-glucosidase; glucoamylase; lysosomal α-glucosidase; 1,4-α-D-glucan glucohydrolase) In addition to cleaving the last α(1-4)glycosidic linkages at the nonreducing end of amylose and amylopectin, yielding glucose, γ-amylase will cleave α(1-6) glycosidic linkages.

Uses

Amylase enzymes are used extensively in bread making to break down complex sugars such as starch (found in flour) into simple sugars. Yeast then feeds on these simple sugars and converts it into the waste products of alcohol and CO₂. This imparts flavour and causes the bread to rise. While Amylase enzymes are found naturally in yeast cells, it takes time for the yeast to produce enough of these enzymes to break down significant quantities of starch in the bread. This is the reason for long fermented doughs such as sour dough. Modern bread making techniques have included amylase enzymes into bread improver thereby making the bread making process faster and more practical for commercial use.

Bacilliary amylase is also used in detergents to dissolve starches from fabrics.

Workers in factories that work with amylase for any of the above uses are at increased risk of occupational asthma. 5-9% of bakers have a positive skin test, and a fourth to a third of bakers with breathing problems are hypersensitive to amylase. ^[1]

An inhibitor of alpha-amylase called phaseolamin has been tested as a potential diet aid. ^[2]

References

1. ^ Mapp CE. Agents, old and new, causing occupational asthma. Occup Environ Med 2001;58:354-60. PMID 11303086.
2. ^ Udani J, Hardy M, Madsen DC. (March 2004). "Blocking carbohydrate absorption and weight loss: a clinical trial using Phase 2 brand proprietary fractionated white bean extract.". Alternative medicine review. 

Burtis, Carl A.; Ashwood, Edward R. (1999). Tietz Textbook of Clinical Chemistry, 3rd ed.. Philadelphia: W. B. Saunders Company, 689-698, 1318. ISBN 0-7216-5610-2. 

External links

• Molecule of the month February 2006 at the Protein Data Bank.
• Nutrition Sciences 101 at University of Arizona.

Hydrolase: sugar hydrolases (EC 3.2)
3.2.1: Glycoside hydrolases	Amylase (Alpha-Amylase) - Chitinase - Lysozyme - Neuraminidase - Galactosidases (Alpha, Beta) - alpha-Mannosidase - Glucuronidase - Hyaluronidase - Pullulanase - Glucocerebrosidase - Galactosylceramidase - Alpha-N-acetylglucosaminidase - Fucosidase - Hexosaminidase - Iduronidase - Disaccharidase (Sucrase/Sucrase-isomaltase/Invertase, Maltase, Trehalase, Lactase) - Glucosidases (Cellulase, Alpha-glucosidase, Beta-glucosidase, Debranching enzyme)
3.2.2: Hydrolysing N-Glycosyl compounds	DNA glycosylases: Oxoguanine glycosylase

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Dansk (Danish)
n. - amylase

Nederlands (Dutch)
amylase (zetmeel afbrekend enzym)

Français (French)
n. - (Physiol) amylase

Deutsch (German)
n. - (chem.) Amylase

Ελληνική (Greek)
n. - (χημ.) αμυλάση

Italiano (Italian)
amilasi

Português (Portuguese)
n. - amilase (f) (Quím.)

Русский (Russian)
амилаза

Español (Spanish)
n. - amilasa

Svenska (Swedish)
n. - amylas

中文（简体） (Chinese (Simplified))
淀粉酵素

中文（繁體） (Chinese (Traditional))
n. - 澱粉酵素

한국어 (Korean)
n. - 아밀라아제

日本語 (Japanese)
n. - アミラーゼ

العربيه (Arabic)
‏(الاسم) الأميليز : خميره في اللعاب والعصاره البنكرياسيه تساعد على تحويل النشا الى سكر‏

עברית (Hebrew)
n. - ‮תסס עמילן (אנזים), אנזים ההופך עמילן וגליקוגן (חומר בכבד) לסוכרים פשוטים‬

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