PURIFICATION AND CHARACTERIZATION OF A BETA-AMYLASE FROM SOYA BEANS

Abstract

1. beta-Amylase obtained by acidic extraction of soya-bean flour was purified by ammonium sulphate precipitation, followed by chromatography on calcium phosphate, diethylaminoethylcellulose, Sephadex G-25 and carboxymethylcellulose. 2. The homogeneity of the pure enzyme was established by criteria such as ultracentrifugation and electrophoresis on paper and in polyacrylamide gel. 3. The pure enzyme had a nitrogen content of 16.3%, its extinction coefficient, E(1%) (1cm.), at 280mmu was 17.3 and its specific activity/mg. of enzyme was 880 amylase units. 4. The molecular weight of the pure enzyme was determined as 61700 and its isoelectric point was pH5.85. 5. Preliminary examinations indicated that glutamic acid formed the N-terminus and glycine the C-terminus. 6. The amino acid content of the pure enzyme was established, one molecule consisting of 617 amino acid residues. 7. The pH optimum for pure soya-bean beta-amylase is in the range 5-6. Pretreatment of the enzyme at pH3-5 decreases enzyme activity, whereas at pH6-9 it is not affected.