Amylase
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[[Image:Salivary alpha-amylase 1SMD.png|thumb|A diagram of an amylase molecule from human saliva. [[Calcium]] [[ion]] visible in pale khaki; [[chloride]] ion in green. From {{PDB|1SMD}}.]]
[[Image:Pancreatic alpha-amylase 1HNY.png|thumb|Human pancreatic amylase. [[Calcium]] [[ion]] visible in pale khaki; [[chloride]] ion in green. From {{PDB|1HNY}}.]]
'''Amylase''' is an [[enzyme]] that breaks [[starch]] down into [[sugar]]. Amylase is present in human [[saliva]], where it begins the chemical process of [[digestion]]. Foods that contain much starch but little sugar, such as as [[rice]] and [[potato]], taste slightly sweet as they are chewed because amylase turns some of their starch into sugar in the mouth. The [[pancreas]] also makes amylase to break down stored [[glycogen]] into [[glucose]] to supply the body with energy. Plants and some bacteria also produce amylase. As ''[[diastase]]'', amylase was the first enzyme to be discovered and isolated (by [[Anselme Payen]] in 1833).{{Fact|date=June 2008}} Specific amylase [[protein]]s are designated by different Greek letters. All amylases are [[glycoside hydrolase]]s and act on α-1,4-[[glycosidic bond]]s.
==Classification==
===α-Amylase===
{{main|alpha-Amylase}}
({{EC number|3.2.1.1 }}) ([[CAS registry number|CAS]]# 9014-71-5) (alternate names: 1,4-α-<small>D</small>-glucan glucanohydrolase; glycogenase)
The α-amylases are [[calcium]] [[metalloprotein|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 [[dextrin|"limit dextrin"]] from [[amylopectin]]. Because it can act anywhere on the [[Substrate (biochemistry)|substrate]], α-amylase tends to be faster-acting than β-amylase. In [[animal]]s, it is a major [[digestion|digestive]] enzyme and its optimum pH is 6.7-7.0. <ref>[http://www.worthington-biochem.com/introbiochem/effectspH.html Effects of pH (Introduction to Enzymes)<!-- Bot generated title -->]</ref>
In human physiology, both the salivary and pancreatic amylases are α-Amylases. They are discussed in much more detail at [[alpha-Amylase]].
Also found in plants (barley) , fungi (ascomycetes and basidiomycetes) and bacteria (Bacillus)
===β-Amylase===
({{EC number|3.2.1.2 }}) (alternate names: 1,4-α-<small>D</small>-glucan maltohydrolase; glycogenase; saccharogen amylase)
Another form of amylase, β-amylase is also synthesized by [[bacteria]], [[fungi]], and [[plant]]s. 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 [[microbe]]s also produce amylase to degrade extracellular starches. [[Animal]] tissues do not contain β-amylase, although it may be present in microrganisms contained within the [[Gastrointestinal tract|digestive tract]].
===γ-Amylase===<!-- This section is linked from [[Flatulence]] -->
({{EC number|3.2.1.3 }}) (alternative names: Glucan 1,4-α-glucosidase; amyloglucosidase; Exo-1,4-α-glucosidase; glucoamylase; lysosomal α-glucosidase; 1,4-α-<small>D</small>-glucan glucohydrolase)
In addition to cleaving the last [[glycosidic bond|α(1-4)glycosidic linkages]] at the nonreducing end of [[amylose]] and [[amylopectin]], yielding [[glucose]], γ-amylase will cleave α(1-6) glycosidic linkages. Unlike the other forms of amylase, γ-amylase is most efficient in acidic environments and has an optimum pH of 3
==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 CO<sub>2</sub>. 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 (often in the form of [[malted barley]]) into [[bread improver]] thereby making the bread making process faster and more practical for commercial use.<ref>{{cite book
| last = Maton
| first = Anthea
| authorlink =
| coauthors = Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright
| title = Human Biology and Health
| publisher = Prentice Hall
| date = 1993
| location = Englewood Cliffs, New Jersey, USA
| pages =
| url =
| doi =
| id =
| isbn = 0-13-981176-1}}</ref>
Bacilliary amylase is also used in [[detergent]]s 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. <ref>Mapp CE. Agents, old and new, causing occupational asthma. ''Occup Environ Med'' 2001;58:354-60. PMID 11303086.</ref>
An inhibitor of alpha-amylase called [[phaseolamin]] has been tested as a potential [[Diet (nutrition)|diet]] aid. <ref>{{cite journal|
title=Blocking carbohydrate absorption and weight loss: a clinical trial using Phase 2 brand proprietary fractionated white bean extract.| url=http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15005645&dopt=Citation|
journal=Alternative medicine review|date=March 2004|author=Udani J, Hardy M, Madsen DC.}}</ref>
==References==
{{reflist|2}}
==External links==
*[http://www.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb74_1.html Molecule of the month] February 2006 at the [[Protein Data Bank]].
*[http://www.nutrition.arizona.edu/nsc101/chap04/ch04.htm Nutrition Sciences 101] at [[University of Arizona]].
{{Glycoside hydrolases}}
[[Category:Chemical pathology]]
[[Category:EC 3.2.1]]
[[Category:Enzymes]]
[[cs:Amyláza]]
[[da:Amylase]]
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[[es:Amilasa]]
[[eo:Amelazo]]
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[[it:Alfa-amilasi]]
[[he:עמילאז]]
[[nl:Amylase]]
[[ja:アミラーゼ]]
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[[oc:Amilasa]]
[[pl:Amylaza]]
[[pt:Amilase]]
[[simple:Amylase]]
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[[uk:Амілаза]]
[[zh:淀粉酶]]