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

Abstract

Glucoamylase I (MW 90,000; N-terminal alanine) was selectively produced by a submerged 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 molecular 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 intermediate 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 glucoamy...