Cereal Chem 43:62 - 79. | VIEW
Wheat Beta-Amylases. II. Characterization.
R. Tkachuk and K. H. Tipples. Copyright 1966 by the American Association of Cereal Chemists, Inc.
Beta-amylase was isolated from wheat flour by a single (NH4)2SO4 fractionation followed by ion-exchange chromatography to yield three components (A, B, and E) which differ only in their electrophoretic behavior and pH optima. The three components are homogeneous by sedimentation, Tiselius electrophoresis, and ion-exchange chromatography criteria. Optimum enzymatic activity occurs at pH of 5.4, 4.6, and 5.2 to 6.2 for A, B, and E components. The sedimentation coefficient at zero concentration is 4.56s, and the diffusion coefficient is 6.48 x 10(-7) cm.2 sec.-1. The partial specific volume, computed from the amino acid composition, is 0.733 ml./g. These data give a molecular weight of 64,200. Amino acid analysis indicated that the beta-amylase components have a similar amino acid composition, except that the E component has a higher glycine and methionine content. All three components are acidic molecules possessing four -SH groups and one S-S bond.