Enzymes catalyzing the hydrolysis of α-1→4 glucosidic linkages of polysaccharides such as glycogen, starch, or their degradation products. Endoamylases attack the α-1→4 linkage at random. A single type of endoamylase is known, i.e., α-amylases (α-1,4-glucan 4-glucanohydrolases), so named, because the reducing hemiacetal group liberated by the hydrolysis has α optical configuration and mutarotates downward. The more common α-amylases include those isolated from human saliva, human, hog and rat pancreas, Bacillus subtilis, B. coagulans, Aspergillus oryzae, A. candidus, Pseudomonas saccharophila, and barley malt. Exoamylases attack the α-1→4 linkages only from the non-reducing outer polysaccharide chain ends. Those breaking every glucosidic bond to produce solely α-glucose are known as glucoamylases (γ-amylases). Those breaking every alternate bond to produce maltose are known as β-amylases (α-1,4-glucan maltohydrolases). Exoamylases are exclusively of vegetable or microbial origin. Reviews: Fischer, Stein, “α-Amylases” and French, “β-Amylases” in The Enzymes Vol. 4, P. D. Boyer et al., Eds., (Academic Press, New York, 2nd ed., 1960) pp 313-343, 345-368; J. A. Thoma et al., ibid. Vol. V (3rd ed., 1971) pp 115-189; W. M. Fogarty, C. T. Kelly, Microbial Enzymes and Bioconversions, A. H. Rose, Ed. (Academic Press, New York, 1980) pp 115-170.
Enzyme derived from swine pancrease. mol wt ≈45,000. Prepn: Caldwell et al., J. Am. Chem. Soc. 74, 4033 (1952).
Usually derived from Bacillus subtilis. Purification: Stein, Fischer, Helv. Chim. Acta 40, 529 (1957).
Mol wt ≈152,000. Prepn: Balls et al., J. Biol. Chem. 173, 9 (1948).
Enzyme (digestive aid).
Digestive Aid; Enzyme; Digestive