Cereal Chem 49:283 - 297.  |  VIEW ARTICLE
Structural Characterization of the Two Forms of Glucoamylase from Aspergillus niger.

D. R. Lineback, L. A. Aira, and R. L. Horner. Copyright 1972 by the American Association of Cereal Chemists, Inc. 

Glucoamylases I [alpha-D-(1-4)-glucan glucohydrolase, E.C. 3.2.1.3] and II from Aspergillus niger were isolated in high purity by chromatography on DEAE-cellulose ion-exchange columns. Glucoamylase I contained 13% total carbohydrate and had a molecular weight of 74,900. Glucoamylase II contained 18% total carbohydrate and had a moleular weight of 54,300. The carbohydrate moieties in both glycoproteins were O-glycosidically linked through mannose to the hydroxyl groups of serine and threonine in the polypeptide chain. Treating the enzymes with alkaline borohydride eliminated a portion of the carbohydrate. The carbohydrate fragment was eluted from a column of Sephadex G-15 at a volume corresponding to that of a trisaccharide. This fragment was unstable in mild acid, decomposing to mannitol and a disaccharide. Evidence indicates that both enzymes contain the same carbohydrate moieties but differ in amino acid composition.