[Effect of pH on the conformation properties and enzyme activity of alpha-amylase from Aspergillus terricola].

The effect of pH values on the conformation state of the protein globule and enzyme activity of alpha-amylase isolated from the culture liquid of the fungus Aspergillus terricola was studied. By the method of dispersion of optical rotation, it was demonstrated that together with the disordered structure the alpha-amylase macromolecule in its native form contained alpha-helix and beta-structures. With a pH change the enzyme macromolecule showed two conformational transformations: with a pH decrease from 4.0 to 2.0 alpha-helix uncoiled, and with a pH increase from 8.0 to 12.0 beta-form degraded. Hydrolytic activity of alpha-amylase was found to vary symbatically with the specific optic rotation in the above pH range.