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Amylase // is an enzyme that catalyses the breakdown of starch into sugars. Amylase is present in human saliva, where it begins the chemical process of digestion. Foods that contain much starch but little sugar, such 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 (alpha amylase) to hydrolyse dietary starch into disaccharides and trisaccharides which are converted by other enzymes to 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).[1] Specific amylase proteins are designated by different Greek letters. All amylases are glycoside hydrolases and act on α-1,4-glycosidic bonds.
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Contents
- 1 Classification
- 1.1 α-Amylase
- 1.2 β-Amylase
- 1.3 γ-Amylase
- 2 Uses
- 3 Hyperamylasemia
- 4 History
- 5 Human evolution
- 6 References
- 7 External links
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Classification[edit]
α-Amylase[edit]
| Alpha-Amylase |
Human salivary amylase: calcium ion visible in pale khaki, chloride ion in green. PDB 1SMD[2] |
| Identifiers |
| EC number |
3.2.1.1 |
| CAS number |
9000-90-2 |
| Databases |
| IntEnz |
IntEnz view |
| BRENDA |
BRENDA entry |
| ExPASy |
NiceZyme view |
| KEGG |
KEGG entry |
| MetaCyc |
metabolic pathway |
| PRIAM |
profile |
| PDB structures |
RCSB PDB PDBe PDBsum |
| Gene Ontology |
AmiGO / EGO |
| Search |
| PMC |
articles |
| PubMed |
articles |
| NCBI |
proteins |
|
Main article: alpha-Amylase
The α-amylases (EC 3.2.1.1 ) (CAS# 9014-71-5) (alternative names: 1,4-α-D-glucan glucanohydrolase; glycogenase) 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, and its optimum pH is 6.7-7.0.[3]
In human physiology, both the salivary and pancreatic amylases are α-amylases. They are discussed in much more detail at alpha-Amylase.
This form is also found in plants, fungi (ascomycetes and basidiomycetes) and bacteria (Bacillus)
β-Amylase[edit]
| Beta-Amylase |
Structure of barley beta-amylase. PDB 2xfr[4] |
| Identifiers |
| EC number |
3.2.1.2 |
| CAS number |
9000-91-3 |
| Databases |
| IntEnz |
IntEnz view |
| BRENDA |
BRENDA entry |
| ExPASy |
NiceZyme view |
| KEGG |
KEGG entry |
| MetaCyc |
metabolic pathway |
| PRIAM |
profile |
| PDB structures |
RCSB PDB PDBe PDBsum |
| Gene Ontology |
AmiGO / EGO |
| Search |
| PMC |
articles |
| PubMed |
articles |
| NCBI |
proteins |
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Another form of amylase, β-amylase (EC 3.2.1.2 ) (alternative names: 1,4-α-D-glucan maltohydrolase; glycogenase; saccharogen 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 maltose, resulting in the sweet flavor of ripe fruit.
Both α-amylase and β-amylase are present in seeds; β-amylase is present in an inactive form 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 microorganisms contained within the digestive tract. The optimum pH for β-amylase is 4.0-5.0[5]
γ-Amylase[edit]
| Gamma-Amylase. Glucan 1,4-alpha-glucosidase |
| Identifiers |
| EC number |
3.2.1.3 |
| CAS number |
9032-08-0 |
| Databases |
| IntEnz |
IntEnz view |
| BRENDA |
BRENDA entry |
| ExPASy |
NiceZyme view |
| KEGG |
KEGG entry |
| MetaCyc |
metabolic pathway |
| PRIAM |
profile |
| PDB structures |
RCSB PDB PDBe PDBsum |
| Gene Ontology |
AmiGO / EGO |
| Search |
| PMC |
articles |
| PubMed |
articles |
| NCBI |
proteins |
|
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) will cleave α(1-6) glycosidic linkages, as well as the last α(1-4)glycosidic linkages at the nonreducing end of amylose and amylopectin, yielding glucose. The γ-amylase has most acidic pH optimum because it is most active around pH 3.
Uses[edit]
Amylases find use in breadmaking and 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 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 as sour dough. Modern breadmaking techniques have included amylases (often in the form of malted barley) into bread improver, thereby making the process faster and more practical for commercial use.[6]
Alpha and beta amylases are important in brewing beer and liquor made from sugars derived from starch. In fermentation, yeast ingest sugars and excrete alcohol. In beer and some liquors, the sugars present at the beginning of fermentation have been produced by "mashing" grains or other starch sources (such as potatoes). In traditional beer brewing, malted barley is 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. This practice is no longer in general use.
When used as a food additive, amylase has E number E1100, and may be derived from swine pancreas or mould mushroom.
Bacilliary amylase is also used in clothing and dishwasher detergents to dissolve starches from fabrics and dishes.
Factory workers who work with amylase for any of the above uses are at increased risk of occupational asthma. Five to 9% of bakers have a positive skin test, and a fourth to a third of bakers with breathing problems are hypersensitive to amylase.[7]
An inhibitor of alpha-amylase, called phaseolamin, has been tested as a potential diet aid.[8]
Blood serum amylase may be measured for purposes of medical diagnosis. A normal concentration is in the range 21-101 U/L. A higher than normal concentration may reflect one of several medical conditions, including acute inflammation of the pancreas (concurrently with the more specific lipase),[9] but also perforated peptic ulcer, torsion of an ovarian cyst, strangulation ileus, macroamylasemia and mumps. Amylase may be measured in other body fluids, including urine and peritoneal fluid.
In molecular biology, the presence of amylase can serve as an additional method of selecting for successful integration of a reporter construct in addition to antibiotic 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 through iodine staining.
Hyperamylasemia[edit]
A January 2007 study from Washington University in St. Louis suggests that saliva tests of the enzyme could be used to indicate sleep debt, as the enzyme increases its activity in correlation with the length of time a subject has been deprived of sleep.[10]
History[edit]
In 1831, Erhard Friedrich Leuchs (1800–1837) described the hydrolysis of starch by saliva, due to the presence of an enzyme in saliva, "ptyalin", an amylase.[11][12] The modern history of enzymes began in 1833, when French chemists Anselme Payen and Jean-François Persoz isolated an amylase complex from germinating barley and named it "diastase".[13][14] In 1862, Alexander Jakulowitsch Danilewsky (1838–1923) separated pancreatic amylase from trypsin.[15][16]
Human evolution[edit]
Carbohydrates are an energy rich food source. Amylase is thought to have played a key role in human evolution in allowing humans an alternative to fruit and protein. A duplication of the pancreatic amylase gene developed independently in humans and rodents, further suggesting its importance. The salivary amylase levels found in the human lineage are six to eight times higher in humans than in chimpanzees, which are mostly fruit eaters and ingest little starch relative to humans.[17]
References[edit]
- ^ (1) Robert Hill and Joseph Needham, The Chemistry of Life: Eight Lectures on the History of Biochemistry (London, England: Cambridge University Press, 1970), page 17 ; (2) Richard B. Silverman, The Organic Chemistry of Enzyme-catalyzed Reactions, 2nd ed. (London, England: Academic Press, 2002), page 1 ; (3) Jochanan Stenesh, Biochemistry, vol. 2 (New York, New York: Plenum, 1998), page 83 ; (4) Robert A. Meyers, ed., Molecular Biology and Biotechnology: A Comprehensive Desk Reference (New York, New York: Wiley-VCH, 1995), page 296.
- ^ Ramasubbu, N.; Paloth, V.; Luo, Y.; Brayer, G. D.; Levine, M. J. (1996). "Structure of Human Salivary α-Amylase at 1.6 Å Resolution: Implications for its Role in the Oral Cavity". Acta Crystallographica Section D Biological Crystallography 52 (3): 435–446. doi:10.1107/S0907444995014119. PMID 15299664. edit
- ^ Effects of pH (Introduction to Enzymes)
- ^ Rejzek, M.; Stevenson, C. E.; Southard, A. M.; Stanley, D.; Denyer, K.; Smith, A. M.; Naldrett, M. J.; Lawson, D. M. et al. (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. PMID 21085740. edit
- ^ "Amylase, Alpha" , I.U.B.: 3.2.1.11,4-α-D-Glucan glucanohydrolase.
- ^ Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1.
- ^ Mapp CE (May 2001). "Agents, old and new, causing occupational asthma". Occup Environ Med 58 (5): 354–60, 290. doi:10.1136/oem.58.5.354. PMC 1740131. PMID 11303086.
- ^ 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". Altern Med Rev 9 (1): 63–9. PMID 15005645.
- ^ http://www.merck.com/mmpe/print/sec02/ch015/ch015b.html
- ^ "First Biomarker for Human Sleepiness Identified", Record of Washington University in St. Louis, January 25, 2007
- ^ Erhard Friedrich Leuchs (1831) "Wirkung des Speichels auf Stärke" (Effect of saliva on starch), Poggendorff's Annalen der Physik und Chemie, vol. 22, page 623 (modern citation: Annalen der Physik, vol. 98, no. 8, page 623). See also: Erhard Friedrich Leuchs (1831) "Über die Verzuckerung des Stärkmehls durch Speichel" (On the saccharification of powdered starch by saliva), Archiv für die Gesammte Naturlehre (Archive for All Science), vol. 21, pages 105-107.
- ^ History of biology 1800–1849
- ^ Anselme Payen and Jean-François Persoz (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
- ^ Danilewsky (1862) "Über specifisch wirkende Körper des natürlichen und künstlichen pancreatischen Saftes" (On the specifically-acting principles of the natural and artificial pancreatic juice), Virchows Archiv für pathologische Anatomie und Physiologie, und für klinische Medizin, vol. 25, pages 279-307. Abstract (in English).
- ^ A History of Fermentation and Enzymes
- ^ American Scientist. March–April 2010.
External links[edit]
- Molecule of the month February 2006 at the Protein Data Bank.
- Nutrition Sciences 101 at University of Arizona.
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Hydrolase: sugar hydrolases (EC 3.2)
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| 3.2.1: Glycoside hydrolases |
| Disaccharidase |
- Sucrase/Sucrase-isomaltase/Invertase
- Maltase
- Trehalase
- Lactase
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| Glucosidases |
- Cellulase
- Alpha-glucosidase
- Acid
- Neutral AB
- Neutral C
- Beta-glucosidase
- Debranching enzyme
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| Other |
- Amylase
- Chitinase
- Lysozyme
- Neuraminidase
- NEU1
- NEU2
- NEU3
- NEU4
- Bacterial neuraminidase
- Viral neuraminidase
- Galactosidases
- alpha-Mannosidase
- Glucuronidase
- Hyaluronidase
- Pullulanase
- Glucosylceramidase
- Galactosylceramidase
- Alpha-N-acetylgalactosaminidase
- Alpha-N-acetylglucosaminidase
- Fucosidase
- Hexosaminidase
- Iduronidase
- Maltase-glucoamylase
- Heparanase
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3.2.2: Hydrolysing
N-Glycosyl compounds |
- DNA glycosylases: Oxoguanine glycosylase
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- B
- enzm
- 1.1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 10
- 11
- 13
- 14
- 15-18
- 2.1
- 3.1
- 4.1
- 5.1
- 6.1-3
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Medical test: Serology, reference range: Clinical biochemistry blood tests (including BMP, CMP) (CPT 82000–84999)
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| Fluid/electrolytes |
- electrolytes
- renal function, BUN-to-creatinine ratio
- Ca
- derived values: Plasma osmolality
- Serum osmolal gap
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| Acid-base |
- Arterial blood gas
- Base excess
- Anion gap
- CO2 content
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| Nutrition |
- Iron tests: Transferrin saturation = Serum iron / Total iron-binding capacity; Ferritin
- Transferrin
- Transferrin receptor
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| Endocrine |
- ACTH stimulation test
- Thyroid function tests
- Blood sugar: Glucose test
- C-peptide
- Fructosamine
- Glycated hemoglobin
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| Metabolic |
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| Cardiovascular |
- Cardiac marker: Troponin test
- CPK-MB test
- LDH
- Myoglobin
- Glycogen phosphorylase isoenzyme BB
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| Digestive |
- Liver function tests: protein tests
- Human serum albumin
- Serum total protein
- ALP
- transaminases
- Bilirubin
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noco/acba/cong/tumr, sysi/epon, urte
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proc/itvp, drug (G4B), blte, urte
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noco (d)/cong/tumr, sysi/epon
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proc, drug (A10/H1/H2/H3/H5)
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noco/cong/tumr, sysi/epon, injr
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proc, drug (C1A/1B/1C/1D), blte
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anat (t, g, p)/phys/devp/enzy
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noco/cong/tumr, sysi/epon
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proc, drug (A2A/2B/3/4/5/6/7/14/16), blte
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