Plants and some bacteria also produce amylase. In human physiology, both the salivary and pancreatic amylases are α-amylases. The optimum pH for β-amylase is 4. The γ-what enzyme is present in potato has most acidic optimum pH of all amylases because it is most active around pH 3. Alpha and beta amylases are important in brewing beer and liquor made from sugars derived from starch.
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 widely in use.
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. Alpha amylase is often listed as an ingredient on commercially package milled flour. E1100, and may be derived from swine pancreas or mould mushroom. 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.
12,000 years ago, human diet began to rely more on plant and animal domestication in place of hunting and gathering. As such, starch became a staple of human diet. Large polymers such as starch are partially hydrolyzed in the mouth by the enzyme amylase before being cleaved further into sugars. Therefore, humans that contained amylase in the saliva would benefit from increased ability to digest starch more efficiently and in higher quantities. This gene, AMY1, originated in the pancreas.
A duplication event of the AMY1 gene allowed it to evolve salivary specificity, leading to the production of amylase in the saliva. In addition 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 possess the same number of copies of the AMY1 gene. Populations known to rely more on carbohydrates have a higher number of AMY1 copies than human populations that, by comparison, consume little starch.
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 population 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. Structure of Human Salivary α-Amylase at 1. 6 Å Resolution: Implications for its Role in the Oral Cavity”. Chemical genetics and cereal starch metabolism: Structural basis of the non-covalent and covalent inhibition of barley β-amylase”. Chew It Up, Spit It Out, Then Brew.
Englewood Cliffs, New Jersey, USA: Prentice Hall. Amylase, a flour additive: an important cause of protein making use of enzymes in industry dermatitis in bakers”. Alpha amylase is a major allergenic component in occupational asthma patients caused by porcine pancreatic extract”. The Association for Clinical Biochemistry and Laboratory Medicine.