Studies on the two forms of amyloglucosidase of Aspergillus niger van Tieghem.

2 isoenzymes of amyloglucosidase, designated as AG-I and AG-II, elaborated exocellularly by a strain of Aspergillus niger van Tieghem, were separated and purified to homogeneity. The enzymes, produced in a selective medium, were separated and purified on a column of DEAE-Sephadex A-50. The mol. wt. of AG-I and AG-II were 69 810 and 89 130, resp. The 2 enzymes were glycoproteins and differed in their carbohydrate contents, pH and temp. stabilities and optima for activity. Their activation energies and Km values also varied. AG-II, had a higher mol. wt., carbohydrate content, increased acid tolerance and was synthesized earlier than AG-I (when the pH of the medium was acid). Hg and Ag salts caused partial inhibition of their activities.