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An amylase () is an enzyme that catalysis the hydrolysis of starch (Latin ) into . Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large amounts of starch but little sugar, such as rice and potatoes, may acquire a slightly sweet taste as they are chewed because amylase degrades some of their starch into sugar. The pancreas and salivary gland make 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. Specific amylase are designated by different Greek letters. All amylases are glycoside hydrolases and act on α-1,4-.
Because it can act anywhere on the substrate, α-amylase tends to be faster-acting than β-amylase. In , it is a major digestion enzyme, and its optimum pH is 6.7–7.0.
In human physiology, both the salivary and pancreatic amylases are α-amylases.
The α-amylase form is also found in plants, fungi (ascomycetes and basidiomycetes) and bacteria ( Bacillus).
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. Many 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.
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 continues to be practiced in home production of some traditional drinks, such as chhaang in the Himalayas, chicha in the Andes and kasiri in Brazil and Suriname.
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 developing dermatitis or asthma.
When used as a food additive, amylase has E number E1100, and may be derived from pig pancreas or mold fungi.
Bacilliary amylase is also used in clothing and dishwasher 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 nine percent of bakers have a positive skin test, and a fourth to a third of bakers with breathing problems are hypersensitive to amylase.
A January 2007 study from Washington University in St. Louis suggests that saliva tests of the enzyme could be used to indicate , as the enzyme increases its activity in correlation with the length of time a subject has been deprived of sleep.
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". It is from this term that all subsequent enzyme names tend to end in the suffix -ase.
In 1862, Russian biochemist (1838–1923) separated pancreatic amylase from trypsin. Abstract (in English).
Following the agricultural revolution 12,000 years ago, human diet began to shift more to plant and animal domestication in place of Hunter-gatherer. 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 as and , who possess either one or no copies of the gene responsible for producing salivary amylase.
Like in other mammals, the pancreatic alpha-amylase AMY2 was duplicated multiple times. One event allowed it to evolve salivary specificity, leading to the production of amylase in the saliva (named in humans as AMY1). The 1p21.1 region of human chromosome 1 contains many copies of these genes, variously named AMY1A, AMY1B, AMY1C, AMY2A, AMY2B, and so on.
However, not all humans possess the same number of copies of the AMY1 gene. 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 of AMY1 gene 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 the Aka people, Datog, and Yakuts.
The correlation that exists between starch consumption and number of AMY1 copies 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 of AMY1 in a high starch population increases fitness and produces healthier, fitter offspring.
This fact is especially apparent when comparing geographically close populations with different eating habits that possess a different number of copies of the AMY1 gene. Such is the case for some Asian populations that have been shown to possess few AMY1 copies 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.
Variations of amylase copy number in dogs mirrors that of human populations, suggesting they acquired the extra copies as they followed humans around. 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.
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