Amylase

AMYLASE, AMYLOLYTIC ENZYME (from Latin amylum - starch, -ase - suffix characterizing enzymes), an enzyme that breaks down starch (see), as well as glycogen, through a series of intermediate stages into maltose (malt sugar). The question of the unity of amylase, i.e., whether the breakdown of starch into maltose occurs under the influence of a single enzyme or a series of sequentially acting enzymes, remains unresolved. Amylases of different origins are apparently not identical—they possess different pH optima, different sensitivity to electrolytes, etc. It is possible, however, that these differences depend on the admixture of various accompanying substances. According to the latest research by Kuhn, there are two types of amylase: α-amylase (e.g., in the pancreas) and β-amylase (e.g., in malt). In starch, which is built from di- and trisaccharide radicals, α-amylase cleaves bonds within these radicals, and β-amylase—between the radicals. Despite such a difference, in both cases, as a result of complex intramolecular rearrangements, one and the same final substance is obtained—maltose. - Properties of amylase. The purest preparation of animal amylase, obtained by Willstätter, did not give a single reaction for protein. The pH optimum for plant amylase (malt) is approx. 5.0; for animal (saliva, pancreas, blood)—approx. 6.8. In the absence of electrolytes, animal amylase completely loses its activity; upon the addition of salts, it is reactivated; chlorides (NaCl) activate it most strongly; plant amylase is apparently less sensitive to electrolytes. The distribution of amylase is extremely wide; it can be detected in almost every cell. The most active amylase is contained in germinating seeds (malt), in saliva, and in pancreatic juice. - Nomenclature. Depending on its location, amylase has received various names: diastase (mainly in seeds), ptyalin (in saliva), amylopsin (in the pancreas), etc. These names are obsolete and should be replaced by the rational term amylase. - Biological significance. Plant and animal (glycogen) starches, by virtue of their colloidal nature, are reserve carbohydrates; in the form of these compounds, the organism stores reserves of potential chemical energy, which can be used only after the conversion of starch into lower-molecular-weight compounds capable of diffusion and chemical reactions, namely—into maltose and further—into glucose. This task is performed by amylase, which mobilizes carbohydrate reserves as needed. The amylase of the digestive tract converts colloidal starch, which is incapable of being absorbed through the intestinal wall, into easily diffusing lower carbohydrates. - Methods for determining amylase are based either on establishing the moment of breakdown of a specific amount of starch, which is judged by the disappearance of the iodine-starch reaction (see Wohlgemuth's method), or on determining the amount of sugar (maltose) formed. The latter methods are significantly more accurate and reliable.