Amylases

Amylases (EC 3.2.1.1; 3.2.1.2; 3.2.1.3) are hydrolase class enzymes with homopolysaccharides as their substrate. Three amylases are known: α-amylase, β-amylase, γ-amylase. They differ in the hydrolysis products formed. α-amylase hydrolyzes the α-1,4-glucosidic linkage in polysaccharides, hence it is also called endoamylase. It has Ca²⁺ in its active site, necessary for enzyme activation. β-amylase releases maltose from starch. β-amylase is an exoamylase. It is also known as maltogenic amylase. It is found in leguminous plants, where it is important for storing reserve starch. γ-amylase releases glucose from the ends of polysaccharide chains. There are neutral and acidic γ-amylases. Acidic γ-amylase is found in lysosomes in human and mammalian organs and tissues, while neutral γ-amylase is found in microsomes and cytoplasm. Salivary amylase is α-amylase. Its hydrolysis initiates the first stages of starch or glycogen breakdown, forming dextrins. There is no amylase in the stomach. The main phases of starch and glycogen hydrolysis occur in the duodenum, where pancreatic α-amylase acts. Starch and glycogen are broken down into maltose. Amylase activity is best in a neutral or weakly alkaline environment.

Source | Glossary of Most Commonly Used Biomedical Terms and Concepts | Lithuanian University of Health Sciences | Academician Professor Antanas Praškevičius, Professor Laima Ivanovienė