Subsite mapping of Aspergillus niger glucoamylases I and II with malto‐ and isomaltooligosaccharides

Glucoamylase, industrially derived from Aspergillus niger, was chromatographically separated into forms I and II and purified to near homogeneity. Preparations were proved to be free of D-glucosyltransferase by electrophoretic and differential inhibition tests. Maximum rates and Michaelis constants were obtained for both glucoamylases I and II with maltooligosaccharides from maltose to maltoheptaose and with isomaltooligosaccharides from isomaltose to isomaltohexaose. Subsite maps were calculated from these kinetic data and were not significantly different for the two forms. Subsites in both forms had lower affinities for D-glucosyl residues contained in isomaltooligosaccharides than for D-glucosyl residues in maltooligosaccharides.