What are?
Amylases are enzymes essential for the digestion of complex carbohydrates, otherwise known as polysaccharides.
Polysaccharides, such as starch and glycogen, are polymers deriving from the aggregation of more than ten simple sugar molecules, such as glucose and fructose.
Amylases are mainly produced by the salivary glands and the exocrine pancreas.
Salivary Amylase - Ptyalin
At the salivary level we find the enzyme commonly called ptyalin, which begins to degrade starch, releasing maltose and dextrins. For this reason, foods rich in starch but low in sugar, such as potatoes, rice or bread, become slightly sweet if chewed for a long time. In general, however, given the scarce permanence of food in the oral cavity, this passage assumes little relevance for digestive purposes.
The optimal pH at which amylases operate varies between 6.7 and 7, which is why ptyalin is slowly inactivated in the decidedly acidic environment of the stomach (pH 1.5-3). This enzyme, moreover, cannot digest the starch contained in granules, which is why it is effective only if the food is cooked. If the starch is raw, the gastric acidity favors the breaking of the granules in which it is enclosed, facilitating the subsequent action of pancreatic amylases.
Pancreatic amylases
The stomach does not produce amylase.
At the duodenal level (first tract of the small intestine), pancreatic juice containing various digestive enzymes, including the aforementioned alpha-amylases, is poured out.
How they work
Pancreatic amylases, like ptyalin, attack the starch glucosidic chain at random sites, alternately splitting α-1,4 (linear) glucosidic bonds, so as to form molecules of maltose and some of glucose.
Amylases, on the other hand, cannot hydrolyze the α-1,6 (branched) bonds present in the structure of amylopectin (remember, briefly, that starch is made up of two glucose polymers, one linear, called amylose, and one containing branching points, called amylopectin).
The amylase action leads to the formation of maltose and glucose starting from "amylose, and maltose, glucose and" limit dextrins "starting from" amylopectin. The latter contain the α-1,6 branching sites which cannot be digested by amylases, they are attacked by specific enzymes, called dextrinases (1,6 glycosidases), present in the brush border. At the same level there are other specific enzymes, capable of digesting disaccharides such as amylose and lactose, releasing mondosaccharides finally available for absorption.
Due to this action, alpha-amylase is widely used in the food industry. In the preparation of bread, for example, this enzyme generates sugars, which are fermented by yeasts with the production of carbon dioxide (very useful for accelerating the leavening process).
High amylases "
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