Alfa-Amylase from germinating soybean (Glycine max) seeds – Purification,characterization and sequential similarity of conserved and catalytic amino acid residues
Abstract
Starch hydrolysing from germinated soybeans seeds (Glycine max) has been purified 400-fold to electrophoretic homogeneity with a final specific activity of 384 units/mg. SDS-PAGE of the final preparation revealed a single protein band of 100 kDa, whereas molecular mass was determined to be 80 kDa by MALDI-TOF and gel filtration on superdex-200 (FPLC). The enzyme exhibited maximum activity at pH 5.5 and a pI value of 4.85. The energy of activation was determined to be 6.09 kcal/mol in the temperature range 25-85 ºC. Apparent michaelis constant (Km(app)) for starch was 0.71 mg/ml and turnover number (kcat) was 280 S-1 in 50 mM sodium acetate buffer, pH 5.5. Thermal in activation studies at 85 ºC showed first-order kinetics with rate constant (k) equal to 0.0063 min-1. Soybean Alfa-amylase showed high specificity for its primary supstrate starch. High similarity of Soybean Alfa-amylase with known amylases suggests that this Alfa-amylase belongs to glycosyl hydrolase family 13. Cereal Alfa-amylase have gained
importance due to their compatibility for biotechnological applications. Wide availability and easy puri- fication protocol make soybean as an attractive alternative for plant alfa-amylase. Soybean can be used as commercially viable source of a-amylase for various industrial applications.