Anamylase(/ˈæmɪleɪs/) is anenzymethatcatalysesthehydrolysisofstarch(Latinamylum) intosugars.Amylase is present in thesalivaof humans and some other mammals, where it begins the chemical process ofdigestion.Foods that contain large amounts of starch but little sugar, such asriceandpotatoes,may acquire a slightly sweet taste as they are chewed because amylase degrades some of their starch into sugar. Thepancreasand salivary gland make amylase (alpha amylase) to hydrolyse dietary starch intodisaccharidesandtrisaccharideswhich are converted by other enzymes toglucoseto supply the body with energy. Plants and some bacteria also produce amylase. Specific amylaseproteinsare designated by different Greek letters. All amylases areglycoside hydrolasesand act on α-1,4-glycosidic bonds.
| Beta-amylase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 | |||||||||
| Identifiers | |||||||||
| EC no. | 3.2.1.2 | ||||||||
| CAS no. | 9000-91-3 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDBstructures | RCSB PDBPDBePDBsum | ||||||||
| Gene Ontology | AmiGO/QuickGO | ||||||||
| |||||||||
| Gamma-amylase. Glucan 1,4-alpha-glucosidase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC no. | 3.2.1.3 | ||||||||
| CAS no. | 9032-08-0 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDBstructures | RCSB PDBPDBePDBsum | ||||||||
| Gene Ontology | AmiGO/QuickGO | ||||||||
| |||||||||
Classification
edit| α-amylase | β-amylase | γ-amylase | |
|---|---|---|---|
| Source | Animals, plants, microbes | Plants, microbes | Animals, microbes |
| Tissue | Salivary gland, pancreas | Seeds, fruits | Small intestine |
| Cleavage site | Random α-1,4 glycosidic bond | Second α-1,4 glycosidic bond | Last α-1,4 glycosidic bond |
| Reaction products | Maltose,dextrin,etc. | Maltose | Glucose |
| Optimum pH | 6.7–7.0 | 5.4–5.5 | 4.0–4.5 |
| Optimum temperature in brewing | 68–74 °C (154–165 °F) | 58–65 °C (136–149 °F) | 63–68 °C (145–154 °F) |
α-Amylase
editThe α-amylases (EC3.2.1.1) (CAS9014–71–5) (alternative names: 1,4-α-D-glucan glucanohydrolase; glycogenase) arecalciummetalloenzymes.By acting at random locations along the starch chain, α-amylase breaks down long-chainsaccharides,ultimately yielding eithermaltotrioseandmaltosefromamylose,or maltose,glucoseand"limit dextrin"fromamylopectin.They belong toglycoside hydrolase family 13(https://www.cazypedia.org/index.php/Glycoside_Hydrolase_Family_13).
Because it can act anywhere on thesubstrate,α-amylase tends to be faster-acting than β-amylase. Inanimals,it is a majordigestiveenzyme, and its optimum pH is 6.7–7.0.[3]
In human physiology, both the salivary and pancreatic amylases are α-amylases.
The α-amylase form is also found in plants, fungi (ascomycetesandbasidiomycetes) and bacteria (Bacillus).
β-Amylase
editAnother form of amylase, β-amylase (EC3.2.1.2) (alternative names: 1,4-α-D-glucan maltohydrolase; glycogenase; saccharogen amylase) is also synthesized bybacteria,fungi,andplants.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 theripeningoffruit,β-amylase breaks starch into maltose, resulting in the sweet flavor of ripe fruit. They belong toglycoside hydrolase family 14.
Both α-amylase and β-amylase are present in seeds; β-amylase is present in an inactive form prior togermination,whereas α-amylase and proteases appear once germination has begun. Manymicrobesalso produce amylase to degrade extracellular starches.Animaltissues do not contain β-amylase, although it may be present in microorganisms contained within thedigestive tract.The optimum pH for β-amylase is 4.0–5.0.[4]
γ-Amylase
editγ-Amylase (EC3.2.1.3) (alternative names: Glucan 1,4-a-glucosidase; amyloglucosidase;exo-1,4-α-glucosidase; glucoamylase; lysosomal α-glucosidase; 1,4-α-D-glucan glucohydrolase) will cleave α(1–6) glycosidic linkages, as well as the last α-1,4 glycosidic bond at the nonreducing end ofamyloseandamylopectin,yieldingglucose.The γ-amylase has the most acidic optimum pH of all amylases because it is most active around pH 3. They belong to a variety of differentglycoside hydrolasefamilies, such asglycoside hydrolase family 15in fungi,glycoside hydrolase family 31of humanMGAM,andglycoside hydrolase family 97of bacterial forms.
Uses
editFermentation
editα- and β-amylases are important inbrewingbeer and liquor made from sugars derived fromstarch.Infermentation,yeastingests sugars and excretesethanol.In beer and some liquors, the sugars present at the beginning of fermentation have been produced by "mashing" grains or other starch sources (such aspotatoes). In traditional beer brewing,malted barleyis mixed with hot water to create a "mash",which is held at a given temperature to allow the amylases in the malted grain to convert the barley's starch into sugars. Different temperatures optimize the activity of alpha or beta amylase, resulting in different mixtures of fermentable and unfermentable sugars. In selecting mash temperature and grain-to-water ratio, a brewer can change the alcohol content,mouthfeel,aroma, and flavor of the finished beer.
In some historic methods of producing alcoholic beverages, the conversion of starch to sugar starts with the brewer chewing grain to mix it with saliva.[5]This practice continues to be practiced in home production of some traditional drinks, such aschhaangin the Himalayas,chichain the Andes andkasiriinBrazilandSuriname.
Flour additive
editAmylases are used inbreadmakingand to break down complex sugars, such as starch (found inflour), into simple sugars.Yeastthen feeds on these simple sugars and converts it into the waste products ofethanolandcarbon dioxide.This imparts flavour and causes the bread to rise. While amylases 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 assourdough.Modern breadmaking techniques have included amylases (often in the form ofmalted barley) intobread improver,thereby making the process faster and more practical for commercial use.[6][failed verification]
α-Amylase is often listed as an ingredient on commercially package-milled flour. Bakers with long exposure to amylase-enriched flour are at risk of developingdermatitis[7]orasthma.[8]
Molecular biology
editInmolecular biology,the presence of amylase can serve as an additional method of selecting for successful integration of a reporter construct in addition toantibiotic resistance.As reporter genes are flanked by homologous regions of the structural gene for amylase, successful integration will disrupt the amylase gene and prevent starch degradation, which is easily detectable throughiodine staining.
Medical uses
editAmylase also has medical applications in the use ofpancreatic enzyme replacement therapy(PERT). It is one of the components in Sollpura (liprotamase) to help in the breakdown ofsaccharidesinto simple sugars.[9]
Other uses
editAn inhibitor of alpha-amylase, calledphaseolamin,has been tested as a potentialdietaid.[10]
When used as afood additive,amylase hasE numberE1100, and may be derived frompigpancreas ormoldfungi.
Bacilliary amylase is also used in clothing and dishwasherdetergentsto dissolve starches from fabrics and dishes.
Factory workers who work with amylase for any of the above uses are at increased risk ofoccupational asthma.Five to nine percent of bakers have a positive skin test, and a fourth to a third of bakers with breathing problems are hypersensitive to amylase.[11]
Hyperamylasemia
editBlood serumamylase may be measured for purposes ofmedical diagnosis.A higher than normal concentration may reflect any of several medical conditions, includingacuteinflammationof thepancreas(which may be measured concurrently with the more specificlipase),[12]perforatedpeptic ulcer,torsion of anovarian cyst,strangulation,ileus,mesenteric ischemia,macroamylasemiaandmumps.Amylase may be measured in other body fluids, includingurineandperitonealfluid.
A January 2007 study fromWashington University in St. Louissuggests that saliva tests of the enzyme could be used to indicatesleep deficits,as the enzyme increases its activity in correlation with the length of time a subject has been deprived of sleep.[13]
History
editIn 1831,Erhard Friedrich Leuchs(1800–1837) described thehydrolysisof starch by saliva, due to the presence of an enzyme in saliva, "ptyalin",an amylase.[14][15]it was named after the Ancient Greek name for saliva:πτύαλον-ptyalon.
The modern history of enzymes began in 1833, when French chemistsAnselme PayenandJean-François Persozisolated an amylase complex from germinating barley and named it "diastase".[16][17]It is from this term that all subsequent enzyme names tend to end in the suffix -ase.
In 1862, Russian biochemistAleksandr Yakovlevich Danilevsky(1838–1923) separated pancreatic amylase fromtrypsin.[18][19]
Evolution
editSalivary amylase
editSaccharidesare a food source rich in energy. Large polymers such as starch are partially hydrolyzed in the mouth by the enzyme amylase before being cleaved further into sugars. Many mammals have seen great expansions in the copy number of the amylase gene. These duplications allow for the pancreatic amylaseAMY2to re-target to the salivary glands, allowing animals to detect starch by taste and to digest starch more efficiently and in higher quantities. This has happened independently in mice, rats, dogs, pigs, and most importantly, humans after the agricultural revolution.[20]
Following theagricultural revolution12,000 years ago, human diet began to shift more to plant and animaldomesticationin place ofhunting and gathering.Starch has become a staple of the human diet.
Despite the obvious benefits, early humans did not possess salivary amylase, a trend that is also seen in evolutionary relatives of the human, such aschimpanzeesandbonobos,who possess either one or no copies of the gene responsible for producing salivary amylase.[21]
Like in other mammals, the pancreatic alpha-amylaseAMY2was duplicated multiple times. One event allowed it to evolve salivary specificity, leading to the production of amylase in the saliva (named in humans asAMY1). The 1p21.1 region of human chromosome 1 contains many copies of these genes, variously namedAMY1A,AMY1B,AMY1C,AMY2A,AMY2B,and so on.[22]
However, not all humans possess the same number of copies of theAMY1gene. Populations known to rely more on saccharides have a higher number of AMY1 copies than human populations that, by comparison, consume little starch. The number ofAMY1gene copies in humans can range from six copies in agricultural groups such as European-American and Japanese (two high starch populations) to only two to three copies in hunter-gatherer societies such as theBiaka,Datog,andYakuts.[22]
The correlation that exists between starch consumption and number ofAMY1copies specific to population suggest that more AMY1 copies in high starch populations has been selected for by natural selection and considered the favorable phenotype for those individuals. Therefore, it is most likely that the benefit of an individual possessing more copies ofAMY1in a high starch population increases fitness and produces healthier, fitter offspring.[22]
This fact is especially apparent when comparing geographically close populations with different eating habits that possess a different number of copies of theAMY1gene. Such is the case for some Asian populations that have been shown to possess fewAMY1copies relative to some agricultural populations in Asia. This offers strong evidence that natural selection has acted on this gene as opposed to the possibility that the gene has spread through genetic drift.[22]
Variations of amylase copy number in dogs mirrors that of human populations, suggesting they acquired the extra copies as they followed humans around.[23]Unlike humans whose amylase levels depend on starch content in diet, wild animals eating a broad range of foods tend to have more copies of amylase. This may have to do with mainly detection of starch as opposed to digestion.[20]
References
edit- ^Ramasubbu N, Paloth V, Luo Y, Brayer GD, Levine MJ (May 1996)."Structure of human salivary alpha-amylase at 1.6 Å resolution: implications for its role in the oral cavity".Acta Crystallographica D.52(3): 435–446.doi:10.1107/S0907444995014119.PMID15299664.
- ^Rejzek M, Stevenson CE, Southard AM, Stanley D, Denyer K, Smith AM, Naldrett MJ, Lawson DM, Field RA (March 2011). "Chemical genetics and cereal starch metabolism: structural basis of the non-covalent and covalent inhibition of barley β-amylase".Molecular BioSystems.7(3): 718–730.doi:10.1039/c0mb00204f.PMID21085740.S2CID45819617.
- ^"Effects of pH (Introduction to Enzymes)".worthington-biochem.com.Retrieved17 May2015.
- ^"Amylase, Alpha, I.U.B.: 3.2.1.11,4-α-D-Glucan glucanohydrolase".
- ^Wadler J (8 September 2009)."Chew It Up, Spit It Out, Then Brew. Cheers!".New York Times.Retrieved27 March2013.
- ^Maton A, Hopkins J, McLaughlin CW, Johnson S, Warner MQ, LaHart D, Wright JD (1993).Human Biology and Health.Englewood Cliffs, NJ: Prentice Hall.ISBN0-13-981176-1.
- ^Morren MA, Janssens V, Dooms-Gossens A, Van Hoeyveld E, Cornelis A, De Wolf-Peeters C, Heremans A (November 1993). "alpha-Amylase, a flour additive: an important cause of protein contact dermatitis in bakers".Journal of the American Academy of Dermatology.29(5 Pt 1): 723–728.doi:10.1016/0190-9622(93)70237-n.PMID8227545.
- ^Park HS, Kim HY, Suh YJ, Lee SJ, Lee SK, Kim SS, Nahm DH (September 2002). "Alpha amylase is a major allergenic component in occupational asthma patients caused by porcine pancreatic extract".The Journal of Asthma.39(6): 511–516.doi:10.1081/jas-120004918.PMID12375710.S2CID23522631.
- ^"Sollpura".Anthera Pharmaceuticals. Archived fromthe originalon 18 July 2015.Retrieved21 July2015.
- ^Udani J, Hardy M, Madsen DC (March 2004)."Blocking saccharide absorption and weight loss: a clinical trial using Phase 2 brand proprietary fractionated white bean extract"(PDF).Alternative Medicine Review.9(1): 63–69.PMID15005645.Archived fromthe original(PDF)on 2011-07-28.
- ^Mapp CE (May 2001)."Agents, old and new, causing occupational asthma".Occupational and Environmental Medicine.58(5): 354–360, 290.doi:10.1136/oem.58.5.354.PMC1740131.PMID11303086.
- ^"Acute Pancreatitis – Gastrointestinal Disorders".Merck Manuals Professional Edition.Merck.[permanent dead link]
- ^"First Biomarker for Human Sleepiness Identified".Record.Washington University in St. Louis.25 January 2007. Archived fromthe originalon 7 October 2007.Retrieved7 July2013.
- ^
- Leuchs EF (1831)."Wirkung des Speichels auf Stärke"[Effect of saliva on starch].Poggendorff's Annalen der Physik und Chemie.22(8): 623.Bibcode:1831AnP....98..623L.doi:10.1002/andp.18310980814.(Modern citation:Annalen der Physik98(8): 623.)
- Leuchs EF (1831)."Über die Verzuckerung des Stärkmehls durch Speichel"[On the saccharification of powdered starch by saliva].Archiv für die gesammte Naturlehre.21:105–107.
- ^"History of Biology: Cuvier, Schwann and Schleiden".pasteur.fr.8 April 2002. Archived fromthe originalon 24 September 2015.Retrieved17 May2015.
- ^Payen A, Persoz JF (1833)."Mémoire sur la diastase, les principaux produits de ses réactions et leurs applications aux arts industriels"[Memoir on diastase, the principal products of its reactions and their applications to the industrial arts].Annales de chimie et de physique.2nd series.53:73–92.
- ^"Industrial Enzymes for Food Production".Archived fromthe originalon 5 December 2008.
- ^Danilewsky AJ (1862)."Über specifisch wirkende Körper des natürlichen und künstlichen pancreatischen Saftes"[On the specifically-acting principles of natural and artificial pancreatic fluid].Virchows Archiv für Pathologische Anatomie und Physiologie und für Klinische Medizin.25:279–307.Abstract (in English).
- ^"A History of Fermentation and Enzymes".navi.net.Archived fromthe originalon 2022-01-10.Retrieved2008-10-25.
- ^abPajic P, Pavlidis P, Dean K, Neznanova L, Romano RA, Garneau D, et al. (May 2019)."Independent amylase gene copy number bursts correlate with dietary preferences in mammals".eLife.8.doi:10.7554/eLife.44628.PMC6516957.PMID31084707.
- ^Vuorisalo T, Arjamaa O (March–April 2010)."Gene-Culture Coevolution and Human Diet".American Scientist.98(2): 140.doi:10.1511/2010.83.140.Archived fromthe originalon 2016-03-04.Retrieved2015-08-15.
- ^abcdPerry 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 (October 2007)."Diet and the evolution of human amylase gene copy number variation".Nature Genetics.39(10): 1256–1260.doi:10.1038/ng2123.PMC2377015.PMID17828263.
- ^Arendt M, Cairns KM, Ballard JW, Savolainen P, Axelsson E (November 2016)."Diet adaptation in dog reflects spread of prehistoric agriculture".Heredity.117(5): 301–306.doi:10.1038/hdy.2016.48.PMC5061917.PMID27406651.
