PURIFICATION AND CHARACTERIZATION OF A β-AMYLASE FROM SOYA BEANS

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Abstract
[beta]-Amylase obtained by acidic extraction of soybean flour was purified by ammonium sulphate precipitation, followed by chromatography on calcium phosphate, diethylaminoethylcellulose, Sephadex G-25, and carboxymethylcellulose. The homogeneity of the pure enzyme was established by criteria such as ultracentrifugation and electrophoresis on paper and in polyacrylamide gel. The pure enzyme had a N content of 16.3%, its extinction coefficient, [image], at 280 m[mu] was 17.3 and its specific activity/mg of enzyme was 880 amylase units. The molecular weight of the pure enzyme was determined to be 61700 and its isoelectric point pH 5.85. Preliminary examinations indicated that glutamic acid formed the N-terminus and glycine the C-terminus. The amino acid content of the pure enzyme was established, 1 molecule consisting of 617 amino acid residues. The pH optimum for pure soybean [beta]-amylase was in the range 5-6. Pretreatment of the enzyme at pH 3-5 decreased enzyme activity, whereas at pH 6-9 it was not affected.