Formation of active derivatives of glucoamylase I during the digestion with fungal acid protease and .ALPHA.-mannosidase.

Glucoamylase I (MW 90, 000; N-terminal alanine) was selectively produced by a sub-merged culture of Aspergillus awamori var. kawachi as an enzyme having the ability to digest even raw starches, and was converted into a modified active glucoamylase decreasing in mole-cular weight during the digestion with the acid protease of the same mold strain. The modified glucoamylase (MW 83, 000; N-terminal alanine plus isoleucine) was resembled to an inter-mediate type of glucoamylase I', and exhibited hydrolysis curves for gelatinized potato starch and maltose in the same manner as that of glucoamylase I; but it did not digest raw starches and was not adsorbed onto cornstarch, and showed the lower hydrolysis limit of 80 percent for glycogen. The carbohydrate contents of glucoamylase I decreased 59 percent during the digestion with fungal α-mannosidase. The carbohydrate-split glucoamylase (MW 86, 000; N-terminal alanine) was unstable at pH 9 or at 65°C in the same extent as glucoamylase I', but was identical with glucoamylase I in the hydrolysis curves for various substrates, the digestibility for raw starches and the adsorbability onto cornstarch. Multiple forms of glucoamylase were observed when native glucoamylase I was degraded stepwisely with fungal acid protease and α-mannosidase.