Amylase, Alpha

Alpha-amylase acts upon large linear polymers at internal bonds. The hydrolytic products have alpha-configuration. The activity is present in all living organisms, however the enzymes vary remarkably even from tissue to tissue within a single species. Plant and animal amylases and those from bacteria and mold have been reviewed by Thoma et al. (1971) and Takagi et al. (1971) respectively.

Characteristics of alpha-Amylase from Hog Pancreas:

Molecular weight: 51,000-54,000 (Cozzone et al. 1970). See also Granger et al. (1975) who indicate the core weight to be 50,000.

Composition: The enzyme is a glycoprotein (Beaupoil-Abadie et al. 1973). Its single polypeptide chain of about 475 residues has two SH groups and four disulfide bridges and contains a tightly bound Ca²⁺. (Granger et al. 1975; Steer et al. 1974). It exists in two forms (I and II) which have identical enzymatic properties, differing only in electrophoretic mobility (Cozzone et al. 1970; Marchis-Mouren and Pasero 1967). Levitzki and Steer (1974) report on a binding site for Cl^- which effects a conformational change that enhances activity. See also Pommier et al. (1974), Telegdi and Straub (1973), Agarwal and Henkin (1987).

Optimum pH: 7.0.

Extinction coefficient: =26 (Caldwell et al. 1952).

Specificity: Alpha-amylase catalyzes the hydrolysis of internal alpha-1,4-glucan links in polysaccharides containing 3 or more alpha-1,4-linked D-glucose units yielding a mixture of maltose and glucose. See also Takeshita and Hehre (1975).

Inhibitors: Urea and other amide reagents (Toralballa and Eitingon 1967).

Activators: Cl^- is essential. (See also O'Donnell et al. 1975 for the effect of bile salts).

Stabilizers: Calcium and chloride ions are necessary for stability.

Stability: Crystalline suspensions in sodium-calcium chloride are stable for several months refrigerated. Solutions in buffered sodium chloride, pH 7.0, are stable for months providing the protein concentration exceeds 0.1%.