2 FORMS OF GLUCOAMYLASE OF ASPERGILLUS NIGER

Two forms of the glucoamylase (α-1,4-glucan glucohydrolase, E.C.3.2.1.3) of Asgillus niger have been purified by chromatography on DEAE-cellulose ion-exchange columns. The purified enzymes possessed a high degree of purity as indicated by paper electrophoresis, sedimentation velocity, and disc-gel electrophoresis. The two enzymes had the same pH optima when starch was used as the substrate, temperature stability at elevated temperatures, action patterns on malto-oligosaccharides, antigenicity, and NH2-terminal amino acid. They differed in electrophoretic mobility, isoelectric point, and, to a small degree, in stability at room temperature for prolonged periods. Glucoamylase I was not dissociable into subunits in the presence of urea, acid, or β-mercaptoethanol under the conditions studied. Both forms of the enzyme were present in the crude glucoamylase preparation and did not arise as artifacts of the purification procedure. © 1969.