[Participation of ions and solutes on the thermostability of alpha-amylase].

Supplement effects of ions, sugars, and amino acids on the thermostability of liquefying type alpha-amylase from Bacillus subtilis were examined. The addition of 1 mmol/L Ca2+ or about 50 mmol/L Na+ remarkably stimulated the thermostability of this enzyme among ions examined. The thermostability of the enzyme was enhanced and reduced by the extrinsic addition of 50 mmol/L acidic amino acid such as glutamic acid and alkaline amino acid of the concentrations of sugars from 0 to 1000 mmol/L the thermostability of alpha-amylase increased almost such as arginine, respectively. With the increases linearly. By the co-existence of Na+ or K+ with some amino acids or sugars the thermostability of this enzyme was fairly increased. The changes in the fluorescence intensity of alpha-amylase were examined as a function of the incubation temperature on the enzyme, which showed a good agreement with those of residual activities.