Amylase
Amylases (from Greek Amylon = cornstarch ) are enzymes that are found in most living organisms and degrade there polysaccharides. Nowadays, α -amylase is also produced by genetic engineering. Their effect is that it (eg starch ) cleave and degrade polysaccharides to the glycoside. Was discovered amylase (then diastase ) in 1833 by the French chemist Anselme Payen in a Malzlösung. Diastase was the first enzyme that was discovered.
Amylase is a hydrolase (an enzyme that cleaves hydrolysis), or classified as a glycosidase ( an enzyme that cleaves polysaccharides ).
Specificity of action
- α -amylase ( EC 3.2.1.1 ) cleaves the α (1-4) - glycosidic linkage of amylose. Characterized dextrins and from maltose, glucose and branched oligosaccharides. In humans, there are five isoforms of the α -amylase, the genes with AMY1A, AMY1B, AMY1C (all three are called salivary amylase ) and AMY2A and AMY2B (both pancreatic amylase ) are named.
- β - amylase (EC 3.2.1.2 ) hydrolyses the chain end thereof from a respective maltose after another. It can therefore act better, the more chain ends are already provided by the α -amylase. This amylase is found in bacteria and plants.
- γ -amylase ( EC 3.2.1.3 ) hydrolyses the chain end thereof in each case a β -D-glucose after the other. Their occurrence is restricted to fungi. Human maltase - glucoamylase in the intestine catalyzes a similar reaction, but not one of the amylases.
- Isoamylases ( EC 3.2.1.68 ) are found only in plants and bacteria and cleave the 1,6 - glycosidic branches of glycogen and amylopectin, similar to the glycogen debranching enzyme.
Effect in the plant kingdom
Amylases are formed during the maturation process in cereal grains and fruits. They convert the starch to sugar to there - this cereal grains can germinate, or fruits are sweet. They are needed to transform the water-insoluble " memory - carbohydrate " strength back into water-soluble single and double sugars (ie, monosaccharides and disaccharides ). Only in this way can the seedling to take them and thus build new cells.
Effect of α -amylases in the human body
The α - amylases in the pancreas (pancreatic amylase) and in the salivary glands of the oral cavity ( salivary amylase ) is formed. In the context of cancer rarely also the detection of amylase from the ovaries and lungs plays a role. The majority of the enzyme is secreted into the digestive tract. With the food absorbed carbohydrates are thus used by the body. Only a fraction enters the bloodstream.
Amylases work like all enzymes only in a certain pH range (from pH 3.5 to pH 9). The optimum of the activity depends on the source of amylases: amylases, which were obtained from fungal cultures have their optimum at pH 5.7, animal and recovered from bacterial cultures amylases exhibit the highest activity rather in the neutral to alkaline region. In the (strong) acid medium they denature, so work with strong secretion of stomach acid ( for protein denaturation ) is not in the stomach. Likewise, fruit acids can inhibit the enzymes. The optimum temperature of the amylase is from about 45 ° C.
Disease symptoms
An increased amylase activity in human blood can be measured at:
- Mumps ( parotitis, coll: goat Peter ), a viral inflammation of the salivary glands
- Acute pancreatitis, because of the damage to the amylase -producing cells
- Chronic pancreatitis
- Abflusstörungen biliary tract ( cholestasis )
- Renal failure, due to decreased clearance
The measurement of the amylase value is easy to perform. He was the main test for pancreatitis, but was supplanted by the measurement of lipase activity partially, but remains an important parameter for evaluation of abdominal pain. Laboratories usually measure either the value of the pancreatic amylase or Gesamtamylase. If only the pancreatic amylase measured, an increased salivary gland diseases by value can not be proven.
Normal values in humans
Depending on the method used, there are significant differences
- Serum Alpha -amylase, total 28-100 U / l
- Alpha-amylase, pancreatic 13-53 U / L
- Alpha-amylase, salivary gland < 47 U / l
- Newborn alpha -amylase, total < 80 U / l
- Spontaneous urine < 460 U / l
- Urine < 270 U / l
Use in food technology
When brewing the naturally occurring enzymes in the grain to be used. Germination is stimulated and interrupted by Darren ( malting ). In the so-called mashing the amylases are used in the temperature and pH optima, the strength of the grain into fermentable single and double sugars from which ferment fermented and / or bottom-fermenting yeasts alcohol and CO2.
Biotechnologically produced amylases ( from bacteria or mold cultures, especially Aspergillus oryzae) are used as flour treatment agent when the flour has too little gas production capacity. Again, caused by the amylases sugars that are converted during fermentation into ethanol and carbon dioxide, and thus let the dough rise. In addition, the biscuits obtained a better browning after treatment. For rye, the Amylasetätigkeit must, inter alia, be counteracted by acidification of the dough to ensure the baking properties of this cereal product (see sourdough).
Use in medicine
Drugs that are mainly based on α -amylases may be used as, inter alia, film-coated tablets for the treatment of mild sore throat, provided they are not accompanied by fever.
Use in dishwashing detergents
In dishwashing detergents (powder, tabs, etc. ) amylase is often included to solve starchy food waste.
Classification
Amylases are the families 13, 14 and 15 in the classification according to Henrissat glycosidases.