It is an enzyme that catalyzes the hydrolysis of starch into sugars.
Amylase is present in the saliva of humans and some other mammals, where the chemical process of digestion begins .
Foods that contain large amounts of starch but little sugar, such as rice and potatoes, may taste slightly sweet as they are chewed because amylase breaks down some of the starch into sugar.
The pancreas and salivary gland produce amylase (alpha amylase) to hydrolyze dietary starch into disaccharides and trisaccharides that other enzymes convert to glucose to supply the body with energy.
Plants and some bacteria also produce amylase. As diastase, amylase was the first enzyme discovered and isolated (by Anselme Payen in 1833).
Specific amylase proteins are designated by different Greek letters. All amylases are glucoside hydrolases and act on α-1,4-glycosidic bonds.
The α-amylases are calcium metalloenzymes. By acting at random locations along the starch chain, α-amylase breaks down long-chain carbohydrates, eventually producing 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 an important digestive enzyme, and its optimum pH is 6.7-7.0.
In human physiology, both salivary and pancreatic amylase are α-amylases.
The α-amylase form is also found in plants, fungi (ascomycetes and basidiomycetes), and bacteria (Bacillus).
Another form of amylase, β-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, separating two glucose (maltose) units at once.
During fruit ripening, β-amylase breaks starch into maltose, resulting in the sweet taste of ripe fruit.
Both α-amylase and β-amylase are present in the seeds; Β-amylase is present in an inactive form before germination, whereas α-amylase and proteases appear after germination has begun.
Many microbes also produce amylase to break down extracellular starches.
Animal tissues do not contain β-amylase, although it may be present in microorganisms contained in the digestive tract. The optimal pH for β-amylase is 4.0-5.0.
Applications
Fermentation
Alpha and beta amylases are important in brewing beer and liquor from sugars derived from starch.
In fermentation, yeast ingest sugars and excrete alcohol. In beer and some spirits, the sugars present at the beginning of fermentation have produced grains or other sources of starch (such as potatoes).
In traditional brewing, malted barley is mixed with hot water to create a “mash”, which is held at a specified temperature to allow the amylases in the malted grain to convert the barley starch into sugars.
Different temperatures optimize alpha or beta amylase activity, resulting in different mixtures of fermentable and non-fermentable sugars.
By selecting the mash temperature and the grain-to-water ratio, a brewer can change the alcohol content, mouthfeel, aroma, and flavor of the finished beer.
In some historical methods of producing alcoholic beverages, the conversion of starch to sugar begins when the brewery chews the grain to mix it with the saliva. This practice is no longer widely used.
Flour additive
Amylases are used in baking and to break down complex sugars, such as starch (found in flour), into simple sugars.
Yeast feeds on these simple sugars and turns them into the waste products of alcohol and CO 2. This imparts flavor and makes the bread rise.
While amylases are naturally found in yeast cells, it takes time for yeast to produce enough of these enzymes to break down significant amounts of starch in bread. This is the reason for long sourdoughs like sour dough.
Modern baking techniques have included amylases (often in the form of malted barley) in the bread improver, making the process faster and more practical for commercial use.
Alpha amylase is often mentioned as an ingredient in commercially ground flour. Bakers with prolonged exposure to amylase-enriched flour are at risk of developing dermatitis or asthma.
Molecular biology
In molecular biology, the presence of amylase can serve as an additional screening method for successful integration of a reporter construct in addition to antibiotic resistance.
As the 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 readily detectable by iodine staining.
Medical uses
Amylase also has medical applications in the use of pancreatic enzyme replacement therapy. It is one of the components in Sollpura (Liprotamase) to aid in the breakdown of carbohydrates into simple sugars.
Other uses
An alpha-amylase inhibitor, called phaseolamin, has been tested as a possible dietary aid.
When used as a food additive, amylase is E number E1100, and can be derived from pig pancreas or mold fungus.
Bacterial amylase is also used in laundry 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 for occupational asthma.
5 to 9% of bakers have a positive skin test, and a quarter to a third of bakers with respiratory problems are hypersensitive to amylase.
hyperamylasemia
Amylase in blood serum can be measured for medical diagnostic purposes.
A higher than normal concentration may reflect one of several medical conditions, including acute inflammation of the pancreas (can be measured at the same time as the more specific lipase), but also perforated peptic ulcer, torsion of an ovarian cyst, strangulation, ileus, ischemia mesenteric, macroamylasemia and mumps.
Amylase can be measured in other body fluids, including urine and peritoneal fluid.
A January 2007 study from Washington University in St. Louis suggests that saliva testing for the enzyme could be used to indicate sleep deficits, as the enzyme increases in activity in correlation with the length of time a subject has been sleep deprived.
Human evolution
Carbohydrates are an energy-rich food source. After the agricultural revolution 12,000 years ago, the human diet began to shift more to the domestication of plants and animals rather than hunting and gathering.
Large polymers such as starch are partially hydrolyzed in the mouth by the enzyme amylase before further cleaving into sugars.
Therefore, humans containing amylase in saliva would benefit from a greater ability to digest starch more efficiently and in greater amounts.
Despite the obvious benefits, early humans did not possess salivary amylase, a trend that is also seen in human evolutionary relatives, such as chimpanzees and bonobos, who possess one or no copy of the gene responsible for producing salivary amylase. .
This gene, AMY1, originated in the pancreas.
A duplication event of the AMY1 gene allowed salivary specificity to evolve, leading to the production of amylase in saliva.
Furthermore, the same event occurred independently in rodents, emphasizing the importance of salivary amylase in organisms that consume relatively large amounts of starch.
However, not all humans have the same number of copies of the AMY1 gene. Populations known to be more carbohydrate dependent have higher AMY1 copy numbers than human populations that consume little starch by comparison.
The number of copies of AMY1 genes in humans can range from six copies in agricultural groups such as European-American and Japanese (two high starch populations) to only 2-3 copies in hunter-gatherer societies such as Biaka, Datog and Yakuts.
The correlation between starch consumption and population-specific copy number of AMY1 suggests that more copies of AMY1 were selected in high-starch populations by natural selection and considered the favorable phenotype for these individuals.
Therefore, the benefit of an individual possessing more copies of AMY1 in a high-starch population is most likely to increase physical fitness and produce fitter and healthier offspring.
This fact is especially evident when geographically close populations with different eating habits that possess a different number of copies of the AMY1 gene are compared.
Such is the case with some Asian populations that they have been shown to have few AMY1 copies relative to a certain agricultural population in Asia.
