Α-Amylase

{{Short description|Enzyme that hydrolyses α bonds of large α-linked polysaccharides}} {{Lowercase title}} {{Use dmy dates|date=November 2021}} {{infobox enzyme | Name = α-Amylase | EC_number = 3.2.1.1 | CAS_number = 9000-90-2 | GO_code = | image = Salivary alpha-amylase 1SMD.png | width = | caption = Human salivary amylase: calcium ion visible in pale khaki, chloride ion in green. PDB {{PDBe|1SMD}}<ref>{{cite journal |vauthors =Ramasubbu N, Paloth V, Luo Y, Brayer GD, Levine MJ |title =Structure of human salivary α-amylase at 1.6 Å resolution: implications for its role in the oral cavity |journal =Acta Crystallographica D |volume =52 |issue =Pt 3 |pages =435–46 |date =May 1996 |pmid =15299664 |doi =10.1107/S0907444995014119 |doi-access =free |bibcode =1996AcCrD..52..435R }}</ref> }}

{{Infobox protein family | Symbol = Alpha-amylase | Name = GH13 catalytic domain | image = PDB 1cyg EBI.jpg | width = | caption = Cyclodextrin glucanotransferase (e.c.2.4.1.19) (cgtase) | Pfam = PF00128 | Pfam_clan = CL0058 | InterPro = IPR006047 | SMART = | PROSITE = | MEROPS = | SCOP = 1ppi | TCDB = | OPM family = 117 | OPM protein = 1wza | CAZy = GH13 | CDD = cd11338 }} {{Infobox protein family | Symbol = Alpha-amyl_C2 | Name = Alpha-amylase C-terminal beta-sheet domain | image = PDB 1rp8 EBI.jpg | width = | caption = Crystal structure of barley alpha-amylase isozyme 1 (amy1) inactive mutant d180a in complex with maltoheptaose | Pfam = PF07821 | Pfam_clan = | InterPro = IPR012850 | SMART = | PROSITE = | MEROPS = | SCOP = | TCDB = | OPM family = | OPM protein = | CAZy = | CDD = }} {{Infobox protein family | Symbol = Alpha-amylase_C | Name = Alpha amylase, C-terminal all-beta domain | image = PDB 5cgt EBI.jpg | width = | caption = maltotriose complex of preconditioned cyclodextrin glycosyltransferase mutant | Pfam = PF02806 | Pfam_clan = CL0369 | InterPro = IPR006048 | SMART = | PROSITE = | MEROPS = | SCOP = 1ppi | TCDB = | OPM family = | OPM protein = | CAZy = | CDD = }}

'''α-Amylase''' is an enzyme ({{EnzExplorer|3.2.1.1}}; systematic name '''4-α-D-glucan glucanohydrolase''') that hydrolyses α bonds of large, α-linked polysaccharides, such as starch and glycogen, yielding shorter chains thereof, dextrins, and maltose, through the following biochemical process:<ref>{{cite web |title=Amylase |url=https://sml.snl.no/amylase |access-date=24 January 2021 |website=Store Medisinske Leksikon |publisher=Store Norske Leksikon |vauthors =Kierulf P }}</ref>

:Endohydrolysis of (1→4)-α-D-glucosidic linkages in polysaccharides containing three or more (1→4)-α-linked D-glucose units

It is the major form of amylase found in humans and other mammals.<ref>{{cite book |vauthors =Voet D, Voet JG |date =2005 |title =Biochimie |edition =2nd |location =Bruxelles |publisher =De Boeck |pages =1583 }}</ref> It is also present in seeds containing starch as a food reserve, and is secreted by many fungi. It is a member of glycoside hydrolase family 13.

== In human biology == Although found in many tissues, amylase is most prominent in pancreatic juice and saliva, each of which has its own isoform of human α-amylase. They behave differently on isoelectric focusing, and can also be separated in testing by using specific monoclonal antibodies. In humans, all amylase isoforms link to chromosome 1p21 (see AMY1A).

=== Salivary amylase (ptyalin) === Amylase is found in saliva and breaks starch into maltose and dextrin. This form of amylase is also called "ptyalin" {{IPAc-en|ˈ|t|aɪ|əl|ɪ|n}}, which was named by chemist Jöns Jacob Berzelius. The name derives from the Greek word πτυω (I spit), because the substance was obtained from saliva.<ref>{{Cite book |last=Berzelius |first=Jöns Jacob |url=https://books.google.com/books?id=Tu4TAAAAQAAJ |title=Traité de chimie: Chimie orgánique |date=1833 |publisher=Firmin Didot |volume=7 |location=Paris, France |page=156 |language=fr |translator=Ms. Esslinger}}</ref> It will break large, insoluble starch molecules into soluble starches (amylodextrin, erythrodextrin, and achrodextrin) producing successively smaller starches and ultimately maltose. Ptyalin acts on linear α(1,4) glycosidic linkages, but compound hydrolysis requires an enzyme that acts on branched products. Salivary amylase is inactivated in the stomach by gastric acid. In gastric juice adjusted to pH 3.3, ptyalin was totally inactivated in 20 minutes at 37 °C. In contrast, 50% of amylase activity remained after 150 minutes of exposure to gastric juice at pH 4.3.<ref name="pmid3652896">{{cite journal |vauthors =Fried M, Abramson S, Meyer JH |title =Passage of salivary amylase through the stomach in humans |journal =Digestive Diseases and Sciences |volume =32 |issue =10 |pages =1097–103 |date =October 1987 |pmid =3652896 |doi =10.1007/bf01300195 |s2cid =24845837 }}</ref> Both starch, the substrate for ptyalin, and the product (short chains of glucose) are able to partially protect it against inactivation by gastric acid. Ptyalin added to buffer at pH 3.0 underwent complete inactivation in 120 minutes; however, addition of starch at a 0.1% level resulted in 10% of the activity remaining, and similar addition of starch to a 1.0% level resulted in about 40% of the activity remaining at 120 minutes.<ref name="pmid2452576">{{cite journal |vauthors =Rosenblum JL, Irwin CL, Alpers DH |title =Starch and glucose oligosaccharides protect salivary-type amylase activity at acid pH |journal =The American Journal of Physiology |volume =254 |issue =5 Pt 1 |pages =G775–80 |date =May 1988 |pmid =2452576 |doi =10.1152/ajpgi.1988.254.5.G775 }}</ref>

==== Optimum conditions for ptyalin ==== : Optimum pH – 7.0;<ref>{{cite web |title=Amylase, Alpha – Worthington Enzyme Manual |url=http://www.worthington-biochem.com/aa/ |url-status=live |archive-url=https://web.archive.org/web/20161014050119/http://www.worthington-biochem.com/aa/ |archive-date=14 October 2016 |website=worthington-biochem.com}}</ref> 5.6-6.9<ref name="casa">{{cite journal |last1=Valls |first1=Cristina |last2=Rojas |first2=Cristina |last3=Pujadas |first3=Gerard |last4=Garcia-Vallve |first4=Santi |last5=Mulero |first5=Miquel |date=July 2012 |title=Characterization of the activity and stability of amylase from saliva and detergent: Laboratory practicals for studying the activity and stability of amylase from saliva and various commercial detergents |journal=Biochemistry and Molecular Biology Education |language=en |volume=40 |issue=4 |pages=254–265 |doi=10.1002/bmb.20612 |pmid=22807429 |s2cid=36680999 |doi-access=free}}</ref> : Human body temperature - 37 degrees Celsius<ref name="casa"/> : Presence of certain anions and activators: :: Chloride and bromide – most effective :: Iodide – less effective :: Sulfate and phosphate – least effective

=== Genetic variation in human salivary amylase === {{further|Amylase#Salivary amylase}} The salivary amylase gene has undergone duplication during evolution, and DNA hybridization studies indicate many individuals have multiple tandem repeats of the gene. The number of gene copies correlates with the levels of salivary amylase, as measured by protein blot assays using antibodies to human amylase. Gene copy number is associated with apparent evolutionary exposure to high-starch diets.<ref name="pmid17828263">{{cite journal |vauthors =Perry GH, Dominy NJ, Claw KG, Lee AS, Fiegler H, Redon R, Werner J, Villanea FA, Mountain JL, Misra R, Carter NP, Lee C, Stone AC |title =Diet and the evolution of human amylase gene copy number variation |journal =Nature Genetics |volume =39 |issue =10 |pages =1256–60 |date =October 2007 |pmid =17828263 |doi =10.1038/ng2123 |pmc =2377015 }}</ref> For example, a Japanese individual had 14 copies of the amylase gene (one allele with 10 copies, and a second allele with four copies). The Japanese diet has traditionally contained large amounts of rice starch. In contrast, a Biaka individual carried six copies (three copies on each allele). The Biaka are rainforest hunter-gatherers who have traditionally consumed a low-starch diet. Perry and colleagues speculated the increased copy number of the salivary amylase gene may have enhanced survival coincident to a shift to a starchy diet during human evolution.

=== Pancreatic amylase === Pancreatic α-amylase randomly cleaves the α(1-4) glycosidic linkages of amylose to yield dextrin, maltose, or maltotriose. It adopts a double displacement mechanism with retention of anomeric configuration. In humans, the salivary amylase evolved from a copy of it.<ref name="pmid17828263"/>

=== In pathology === The test for amylase is easier to perform than that for lipase, making it the primary test used to detect and monitor pancreatitis. Medical laboratories will usually measure either pancreatic amylase or total amylase. If only pancreatic amylase is measured, an increase will not be noted with mumps or other salivary gland trauma.

However, because of the small amount present, timing is critical when sampling blood for this measurement. Blood should be taken soon after a bout of pancreatitis pain, otherwise it is excreted rapidly by the kidneys.

Salivary α-amylase has been used as a biomarker for stress<ref>{{cite journal |vauthors =Noto Y, Sato T, Kudo M, Kurata K, Hirota K |title =The relationship between salivary biomarkers and state-trait anxiety inventory score under mental arithmetic stress: a pilot study |journal =Anesthesia and Analgesia |volume =101 |issue =6 |pages =1873–6 |date =December 2005 |pmid =16301277 |doi =10.1213/01.ANE.0000184196.60838.8D |doi-access =free |s2cid =22252878 }}</ref><ref>{{cite journal |vauthors =Granger DA, Kivlighan KT, el-Sheikh M, Gordis EB, Stroud LR |title =Salivary α-amylase in biobehavioral research: recent developments and applications |journal =Annals of the New York Academy of Sciences |volume =1098 |issue =1 |pages =122–44 |date =March 2007 |pmid =17332070 |doi =10.1196/annals.1384.008 |bibcode =2007NYASA1098..122G |s2cid =222075003 }}</ref> and as a surrogate marker of sympathetic nervous system (SNS) activity<ref>{{cite journal |vauthors =Nater UM, Rohleder N |title =Salivary α-amylase as a non-invasive biomarker for the sympathetic nervous system: current state of research |journal =Psychoneuroendocrinology |volume =34 |issue =4 |pages =486–96 |date =May 2009 |pmid =19249160 |doi =10.1016/j.psyneuen.2009.01.014 |s2cid =7564969 }}</ref> that does not require a blood draw.

==== Interpretation ==== Increased plasma levels in humans are found in: * Salivary trauma (including anaesthetic intubation) * Mumps – due to inflammation of the salivary glands * Pancreatitis – because of damage to the cells that produce amylase * Kidney failure – due to reduced excretion

Total amylase readings of over 10 times the upper limit of normal (ULN) are suggestive of pancreatitis. Five to 10 times the ULN may indicate ileus or duodenal disease or kidney failure, and lower elevations are commonly found in salivary gland disease.

=== Genes === * salivary – ''AMY1A'', ''AMY1B'', ''AMY1C'' * pancreatic – ''AMY2A'', ''AMY2B''

== In grain == α-Amylase activity in grain is measured by, for instance, the Hagberg–Perten Falling Number, a test to assess sprout damages,<ref> {{Cite web |year=2005 |title=Falling Number – Introduction |url=http://www.perten.com/pages/ProductPage____367.aspx?epslanguage=EN&gclid=CL7P2tuq9JYCFSXlXgodginnXw |url-status=dead |archive-url=https://web.archive.org/web/20090909073254/http://www.perten.com/pages/ProductPage____367.aspx?epslanguage=EN |archive-date=9 September 2009 |access-date=21 November 2009 |publisher=Perten Instruments }} </ref> or the Phadebas method. It occurs in wheat.<ref name="Gatehouse-et-al-1997" />

== Industrial use == α-Amylase is used in ethanol production to break starches in grains into fermentable sugars.

The first step in the production of high-fructose corn syrup is the treatment of cornstarch with α-amylase, which cleaves the long starch polymers into shorter chains of oligosaccharides.

An α-amylase called "Termamyl", sourced from ''Bacillus licheniformis'', is also used in some detergents, especially dishwashing and starch-removing detergents.<ref> {{Cite web |date=20 December 2004 |title=The use of enzymes in detergents |url=http://www1.lsbu.ac.uk/biology/enztech/detergent.html |url-status=dead |archive-url=https://web.archive.org/web/20091020180115/http://www1.lsbu.ac.uk/biology/enztech/detergent.html |archive-date=20 October 2009 |access-date=21 November 2009 |publisher=Faculty of Engineering, Science and the Built Environment, London South Bank University }} </ref>

See amylase for more uses of the amylase family in general.

== Potential for medical use == α-Amylase has exhibited efficacy in degrading polymicrobial bacterial biofilms by hydrolyzing the α(1→4) glycosidic linkages within the structural, matrix exopolysaccharides of the extracellular polymeric substance (EPS).<ref>{{cite journal |vauthors =Fleming D, Rumbaugh KP |title =Approaches to Dispersing Medical Biofilms |journal =Microorganisms |volume =5 |issue =2 |date =April 2017 |pmid =28368320 |doi =10.3390/microorganisms5020015 |doi-access =free |pmc =5488086 |page =15 }}</ref><ref>{{cite journal |vauthors =Fleming D, Chahin L, Rumbaugh K |title =Glycoside Hydrolases Degrade Polymicrobial Bacterial Biofilms in Wounds |journal =Antimicrobial Agents and Chemotherapy |volume =61 |issue =2 |pages =AAC.01998–16 |date =February 2017 |article-number =e01998-16 |pmid =27872074 |doi =10.1128/AAC.01998-16 |pmc =5278739 }}</ref>

== Disease and health relevance == * '''Diabetes:''' α-glucosidase and α-amylase inhibitors are found in several raw plants/herbs such as cinnamon<ref name=":0">{{Cite journal |last1=Moreira |first1=Fernanda Duarte |last2=Reis |first2=Caio Eduardo Gonçalves |last3=Gallassi |first3=Andrea Donatti |last4=Moreira |first4=Daniel Carneiro |last5=Welker |first5=Alexis Fonseca |date=2024-10-09 |editor-last=Dardari |editor-first=Dured |title=Suppression of the postprandial hyperglycemia in patients with type 2 diabetes by a raw medicinal herb powder is weakened when consumed in ordinary hard gelatin capsules: A randomized crossover clinical trial |journal=PLOS ONE |language=en |volume=19 |issue=10 |article-number=e0311501 |bibcode=2024PLoSO..1911501M |doi=10.1371/journal.pone.0311501 |issn=1932-6203 |pmc=11463819 |pmid=39383145 |doi-access=free}}</ref> and bacteria containing acarbose<ref>{{Cite journal |last1=Hayward |first1=Nicholas J. |last2=McDougall |first2=Gordon J. |last3=Farag |first3=Sara |last4=Allwood |first4=J. William |last5=Austin |first5=Ceri |last6=Campbell |first6=Fiona |last7=Horgan |first7=Graham |last8=Ranawana |first8=Viren |date=December 2019 |title=Cinnamon Shows Antidiabetic Properties that Are Species-Specific: Effects on Enzyme Activity Inhibition and Starch Digestion |journal=Plant Foods for Human Nutrition |language=en |volume=74 |issue=4 |pages=544–552 |bibcode=2019PFHN...74..544H |doi=10.1007/s11130-019-00760-8 |issn=0921-9668 |pmc=6900266 |pmid=31372918}}</ref> They are used as anti-diabetic drugs. The intake of a single dose of before a meal containing complex carbohydrates clearly suppresses the glucose spike and may decrease the postprandial hyperglycemia (higher than 140 mg/dL; >7.8 mmol/L) in patients with type II diabetes.<ref name=":0" />

== Buffer inhibition == The tris molecule is reported to inhibit a number of bacterial α-amylases,<ref name="g">{{cite journal |vauthors =Ghalanbor Z, Ghaemi N, Marashi SA, Amanlou M, Habibi-Rezaei M, Khajeh K, Ranjbar B |title =Binding of Tris to Bacillus licheniformis alpha-amylase can affect its starch hydrolysis activity |journal =Protein and Peptide Letters |volume =15 |issue =2 |pages =212–4 |pmid =18289113 |doi =10.2174/092986608783489616 |year =2008 }}</ref><ref name="aghaj">{{cite journal |vauthors =Aghajari N, Feller G, Gerday C, Haser R |title =Crystal structures of the psychrophilic α-amylase from Alteromonas haloplanctis in its native form and complexed with an inhibitor |journal =Protein Science |volume =7 |issue =3 |pages =564–72 |date =March 1998 |pmid =9541387 |doi =10.1002/pro.5560070304 |pmc =2143949 }}</ref> so they should not be used in tris buffer.

==Determination== Several methods are available for determination of α-amylase activity, and different industries tend to rely on different methods. The starch iodine test, a development of the iodine test, is based on colour change, as α-amylase degrades starch and is commonly used in many applications. A similar but industrially produced test is the Phadebas amylase test, which is used as a qualitative and quantitative test within many industries, such as detergents, various flour, grain, and malt foods, and forensic biology.

Modified colorimetric microdetermination of amylase is described in which the digestion of starch is measured by the decrease in the starch-iodine color.<ref>{{Cite journal |last=Pimstone |first=Neville R. |date=1964 |title=A Study of the Starch-Iodine Complex: A Modified Colourimetric Micro Determination of Amylase in Biological Fluids |url=https://academic.oup.com/clinchem/article-abstract/10/10/891/5672826 |url-status=live |journal=Clinical Chemistry |publisher=American Association for Clinical Chemistry |volume=10 |issue=10 |pages=891–906 |doi=10.1093/clinchem/10.10.891 |url-access=subscription |archive-url=https://web.archive.org/web/20220514124654/https://academic.oup.com/clinchem/article-abstract/10/10/891/5672826 |archive-date=14 May 2022 |doi-access=free}}</ref>

==Domain architecture== α-Amylases contain a number of distinct protein domains. The catalytic domain has a structure consisting of an eight-stranded α/β barrel that contains the active site, interrupted by a ~70-amino acid calcium-binding domain protruding between β-strand 3 and α-helix 3, and a carboxyl-terminal Greek key β-barrel domain.<ref name="pmid16302977">{{cite journal |vauthors =Abe A, Yoshida H, Tonozuka T, Sakano Y, Kamitori S |title =Complexes of ''Thermoactinomyces vulgaris'' R-47 alpha-amylase 1 and pullulan model oligossacharides provide new insight into the mechanism for recognizing substrates with α-(1,6) glycosidic linkages |journal =The FEBS Journal |volume =272 |issue =23 |pages =6145–53 |date =December 2005 |pmid =16302977 |doi =10.1111/j.1742-4658.2005.05013.x |doi-access =free |s2cid =41008169 }}</ref> Several α-amylases contain a β-sheet domain, usually at the C terminus. This domain is organised as a five-stranded antiparallel β-sheet.<ref name="pmid9571044">{{Cite journal |last1=Kadziola |first1=Anders |last2=Søgaard |first2=Morten |last3=Svensson |first3=Birte |last4=Haser |first4=Richard |date=April 1998 |title=Molecular structure of a barley α-amylase-inhibitor complex: implications for starch binding and catalysis |url=https://linkinghub.elsevier.com/retrieve/pii/S0022283698916837 |journal=Journal of Molecular Biology |language=en |volume=278 |issue=1 |pages=205–217 |doi=10.1006/jmbi.1998.1683 |pmid=9571044 |url-access=subscription }}</ref><ref name="pmid8196040">{{Cite journal |last1=Kadziola |first1=Anders |last2=Abe |first2=Jun-ichi |last3=Svensson |first3=Birte |last4=Haser |first4=Richard |date=May 1994 |title=Crystal and Molecular Structure of Barley α-Amylase |url=https://linkinghub.elsevier.com/retrieve/pii/S0022283684713544 |journal=Journal of Molecular Biology |language=en |volume=239 |issue=1 |pages=104–121 |doi=10.1006/jmbi.1994.1354 |pmid=8196040 |url-access=subscription }}</ref> Several α-amylases contain an all-β domain, usually at the C terminus.<ref name="pmid7877175">{{cite journal |vauthors =Machius M, Wiegand G, Huber R |title =Crystal structure of calcium-depleted ''Bacillus licheniformis'' α-amylase at 2.2 Å resolution |journal =Journal of Molecular Biology |volume =246 |issue =4 |pages =545–59 |date =March 1995 |pmid =7877175 |doi =10.1006/jmbi.1994.0106 }}</ref>

== See also == * Alpha-glucosidase inhibitor * Acarbose * Cinnamon * Digestive enzyme

== References == {{Reflist|2|refs=

<ref name="Gatehouse-et-al-1997">{{cite journal |year=1997 |title=Transgenic potato plants with enhanced resistance to the tomato moth, ''Lacanobia oleracea'': growth room trials |journal=Molecular Breeding |publisher=Springer Science+Business |volume=3 |issue=1 |pages=49–63 |bibcode=1997MBree...3...49G |doi=10.1023/a:1009600321838 |issn=1380-3743 |s2cid=23765916 |vauthors =Gatehouse AM, Davison GM, Newell CA, Merryweather A, Hamilton WD, Burgess EP, Gilbert RJ, Gatehouse JA }}</ref>

}}

== External links == * {{usurped|1=[https://web.archive.org/web/20071206141528/http://macromoleculeinsights.com/alphaamylase.php The alpha-Amylase Protein]}} * {{MeshName|alpha-Amylase}}

Category:EC 3.2.1 Category:Enzymes Category:Enzymes of known structure