Amylases

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Amylases
Amylases
Salivary amylase; green = chloride ion, yellow = calcium ion
Enzyme classification
EC, category 3.2.1. ,  Glycosidases
Response type hydrolysis
Substrate Polysaccharides

Amylases (from ancient Greek ἄμυλον ámylon "starch") are enzymes that occur in most living things and break down polysaccharides there . Nowadays α-amylase is also produced by genetic engineering. Their effect is that they break down and break down polysaccharides (e.g. starch ) at the glycoside bonds.

Amylase is classified as a hydrolase (an enzyme that splits hydrolytically) or as a glycosidase (an enzyme that splits polysaccharides).

history

Amylase was discovered in 1811 by the German pharmacist Constantin Kirchhoff in St. Petersburg. Because of the continental blockade imposed on British colonial goods by Napoleon, sugar cane had become scarce across Europe. There was a feverish search for chemical methods to produce sugar directly from starch . With the intention of producing a substitute for gum arabic , Kirchhoff succeeded in unintentionally producing larger amounts of a sugar by boiling starch with dilute sulfuric acid. It was the first discovery and immediate use of a chemical process of breaking starch without the involvement of microorganisms. At that time it was unknown that the action of the microorganisms is based on ingredients that are now called enzymes. Erhard Friedrich Leuchs discovered in 1831 that the human saliva apparently saccharifies starch.

The two French chemists Anselme Payen and Jean-Francois Persoz refined the process of sugar production from starch in a sugar factory near Paris in 1833. They were convinced that it was a "simple chemical" process and that the sugar was simply separated from the starch; hence they called this process diastasis (Greek for to separate). In 1835, the Swedish chemist Jöns Jakob Berzelius suspected diastase to be a chemical process with the action of catalytic forces. At the beginning of the 20th century, the now outdated term "diastase" was no longer used to designate the chemical process according to Payen, but was synonymous with the term "amylase", which is used today, to rather name enzymes that hydrolyze starch in Catalyze sugar.

In the following years, the identification and naming of enzymes by Eduard Buchner , Robert Koch , and Wilhelm Kühne , and the chemical characterization by John Howard Northrop . The latter proved that enzymes can consist entirely of 'pure' protein.

In 1925 Richard Kuhn's enzymes were named α-amylases , the products of which are in the α configuration. In 1930 Ohlsson discovered another amylase, the product being β-mannose. In 1971 Kamaryt located the locus for the genes of the human amylase enzymes on the 1st chromosome. The crystal structure of α-amylase was isolated from the Aspergillus oryzae mold and elucidated by Matsuura in 1979. The amino acid sequence of α-amylase was published by Kluh et al. 1981 and Pasero et al. 1986 presented, the complete chromosomal DNA sequence was then 1999 by Darnis et al. enlightened.

Effect specificity

  • α-Amylase ( EC  3.2.1.1 ) cleaves internal α (1-4) -glycoside bonds of amylose , but not terminal or α (1-6) -glycoside bonds. This creates maltose , maltotriose and branched oligosaccharides . There are five isoforms of α-amylase in humans , the genes of which are named AMY1A , AMY1B , AMY1C (all three are called salivary amylase ) and AMY2A and AMY2B (both pancreatic amylase ).
  • β-Amylase ( EC  3.2.1.2 ) splits off one maltose molecule after the other from the chain end. It can therefore work better, the more chain ends have already been created by the α-amylase. This amylase is found in bacteria and plants.
  • γ-Amylase ( EC  3.2.1.3 ) splits off one β-D-glucose after the other from the chain end. Their occurrence is limited to mushrooms. The human maltase glucoamylase in the intestine catalyzes a similar reaction, but is not an amylase.
  • Isoamylases ( EC  3.2.1.68 ) occur only in plants and bacteria and split the 1,6-glycosidic branches of glycogen and amylopectin , similar to the glycogen debranching enzyme .

Effect in the plant kingdom

Amylases are formed in cereal grains and fruits during the ripening process . There they convert the starch into sugar - which allows cereal grains to germinate and fruits to become sweeter. They are necessary to convert the water-insoluble "storage carbohydrate" starch back into water-soluble single and double sugars ( mono- and disaccharides ). Only in this form can the seedling absorb them and build new cells.

Effect of α-amylases in the human body

The α-amylases are produced in the pancreas ( pancreatic amylase ) and in the salivary glands of the oral cavity ( salivary amylase ). In the context of cancer diagnosis , the detection of amylase from the ovaries and the lungs also rarely plays a role. Most of the enzyme is released into the digestive tract. Carbohydrates ingested with food can be used by the body. Only a fraction gets into the blood.

pH value and temperature optimum

Like all enzymes, amylases only work in a certain pH range (pH 3.5 to pH 9). The optimum activity depends on the origin of the amylases: Amylases obtained from fungal cultures have their optimum at pH 5.7, while animal amylases and amylases obtained from bacterial cultures tend to have the highest activity in the neutral to alkaline range. They denature in a (strongly) acidic environment and do not work if there is a strong release of stomach acid (for protein denaturation) in the stomach. Fruit acids can also inhibit the enzymes. The optimum temperature for amylases is around 45 ° C.

Disease symptoms

Increased amylase activity in human blood can be measured at

The measurement of the amylase value is easy to carry out. It was the main test for pancreatitis, but has been partially supplanted by the measurement of lipase activity. However, their values ​​remain an important parameter for clarifying upper abdominal complaints. In the laboratory, either the level of pancreatic amylase or total amylase is measured. However, if the pancreatic amylase alone is measured, an increased value due to salivary gland diseases cannot be detected.

Normal values ​​in humans

There are considerable differences depending on the method used.

  • serum
    • Alpha-amylase, total 28-100 U / L
    • Alpha-amylase, pancreas 13-53 U / l
    • Alpha-amylase, salivary gland <47 U / l
    • Newborn alpha amylase, total <80 U / L
  • Urine (measurement 37 ° C)
    • Spontaneous urine <460 U / l
    • Collective urine <270 U / l

Use in food technology

Barley malt (= germinating brewer's barley). Maltose is produced during malting .

The enzymes naturally occurring in the grain work when brewing beer . Germination is stimulated and interrupted by drying ( malting ). During mashing, the amylases are used in the temperature and pH value optima to convert the starch of the grain into fermentable single and double sugars , from which the top-fermented or bottom-fermented yeasts ferment alcohol and CO 2 .

Biotechnologically produced amylases (from bacteria or mold cultures , especially Aspergillus oryzae ) are used as flour treatment agents when the flour has too little gas formation capacity. The amylases produce sugars, which are converted into ethanol and carbon dioxide during fermentation and thus allow the dough to rise better. In addition, the baked goods are better browned after the treatment. On the other hand, in the case of rye, the amylase activity must be counteracted by acidifying the dough in order to ensure the baking ability of this cereal product (see sourdough ).

Use in medicines

Medicines that are mainly based on α-amylases are used as film-coated tablets, among other things, for the treatment of mild sore throats that are not accompanied by fever.

Use in dishwashing detergents and detergents

In machine dishwashing detergents (powder and tabs) and laundry detergents , amylase is often used to dissolve starchy food residues.

classification

According to Henrissat, amylases form families 13, 14 and 15 in the classification of glycosidases.

Risk assessment

In 2014, α-amylase was included in the EU's ongoing action plan ( CoRAP ) in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation . The effects of the substance on human health and the environment are re-evaluated and, if necessary, follow-up measures are initiated. The reasons for the uptake of α-amylase were concerns about consumer use and exposure of workers as well as the suspected dangers of sensitizing properties. The re-evaluation started in 2015 and was carried out by the United Kingdom . A final report was then published.

Web links

Wiktionary: Amylase  - explanations of meanings, word origins, synonyms, translations
Wikibooks: Biochemistry and Pathobiochemistry: Glycogenolysis and Starch Breakdown  - Learning and Teaching Materials

Individual evidence

  1. ↑ amylase. In: BIOETYMOLOGY. Retrieved February 11, 2020 .
  2. ↑ Perspectives on green genetic engineering through research and development (PDF; 1.5 MB).
  3. ^ Wilhelm Völksen: The discovery of starch saccharification (acid hydrolysis) by GSC Kirchhoff in 1811 . Ed .: Starch. No. 2 , 1949.
  4. ↑ Erhard Friedrich Leuchs: Effect of saliva on strength . Ed .: Poggendorff's Annalen der Physik und Chemie. tape 22 .
  5. ↑ N. Gurung, S. Ray, S. Bose, V. Rai: A broader view: microbial enzymes and their relevance in industries, medicine, and beyond. In: BioMed research international. Volume 2013, 2013, p. 329121, doi: 10.1155 / 2013/329121 , PMID 24106701 , PMC 3784079 (free full text) (review).
  6. ^ Definition of diastasis. Retrieved October 14, 2016 .
  7. ^ Worthington Biochemistry Dictionnary: Amylase, Alpha. Retrieved October 14, 2016 .
  8. ↑ Omim: Alpha Amylase. Retrieved October 14, 2016 .
  9. ↑ J. Kamarýt, R. Adámek, M. Vrba: Possible linkage between uncoiler chromosome Un 1 and amylase polymorphism Amy 2 loci . In: Human Genetics . tape 11 , no. 3 , January 1, 1971, p. 213-220 , PMID 5101659 .
  10. ↑ Randall J. Weselake, Alexander W. MacGregor, Robert D. Hill: An Endogenous α-Amylase Inhibitor in Barley Kernels . In: Plant Physiology . 72, No. 3, Jan. 1, 1983, pp. 809-812. JSTOR 4268117
  11. ↑ Joyce A. Gana, Newton E. Kalengamaliro, Suzanne M. Cunningham, Jeffrey J. Volenec: Expression of β-amylase from Alfalfa Taproots . In: Plant Physiology . 118, No. 4, Jan. 1, 1998, pp. 1495-1505. JSTOR 4278583
  12. ↑ ENZYME entry 3.2.1.3 . Retrieved February 16, 2016.
  13. ↑ D. French, DW Knapp: The maltase of Clostridium acetobutylicum . In: J. Biol. Chem. . 187, 1950, pp. 463-471. PMID 14803428 .
  14. ↑ B. Illingworth Brown, DH Brown: The subcellular distribution of enzymes in type II glycogenosis and the occurrence of an oligo-α-1,4-glucan glucohydrolase in human tissues . In: Biochim. Biophys. Acta . 110, 1965, pp. 124-133. doi : 10.1016 / s0926-6593 (65) 80101-1 . PMID 4286143 .
  15. ↑ PL Jeffrey, DH Brown, BI Brown: Studies of lysosomal α-glucosidase. I. Purification and properties of the rat liver enzyme . In: Biochemistry . 9, 1970, pp. 1403-1415. doi : 10.1021 / bi00808a015 . PMID 4313883 .
  16. ↑ JJ Kelly, DH Alpers: Properties of human intestinal glucoamylase . In: Biochim. Biophys. Acta . 315, 1973, pp. 113-122. doi : 10.1016 / 0005-2744 (73) 90135-6 . PMID 4743896 .
  17. ↑ KD Miller, WH Copeland: A blood trans -α-glucosylase . In: Biochim. Biophys. Acta . 22, 1956, pp. 193-194. doi : 10.1016 / 0006-3002 (56) 90242-6 . PMID 13373867 .
  18. ↑ Y. Tsujisaka, J. Fukimoto, T. Yamamoto: Specificity of crystalline saccharogenic amylase of molds . In: Nature . 181, 1958, pp. 770-771. doi : 10.1038 / 181770a0 . PMID 13517301 .
  19. ↑ ENZYME entry 3.2.1.68 . Retrieved February 16, 2016.
  20. ↑ Kozi Yokobayashi, Akira Misaki, Tokuya Harada: Purification and properties of pseudomonas isoamylase . In: Biochimica et Biophysica Acta (BBA) - Enzymology . 212, No. 3, September 16, 1970, pp. 458-469. doi : 10.1016 / 0005-2744 (70) 90252-4 .
  21. ↑ a b Ternes, Täufel, Tunger, Zobel: Food Lexicon . Behr's Verlag, 4th edition, 2005, ISBN 3-89947-165-2 .
  22. ↑ C. Bessler: The alpha-amylase from Bacillus amyloliquefaciens: improvement of alkali activity and increase of specific activity by means of directed evolution . Dissertation, University of Stuttgart, 2002
  23. ↑ Bernard Henrissat: Glycosyl hydrolase families: classification and list of entries .
  24. ^ Substance Evaluation Conclusion and Evaluation Report . European Chemicals Agency (ECHA)
  25. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): Amylase, α- , accessed on May 20, 2019.