Studies on the Two Forms of Amyloglucosidase of Aspergillus niger van Tieghem

Abstract

Two isoenzymes of amyloglucosidase, designated as AG‐I and AG‐II, elaborated exocellularly by a strain of Aspergillus niger van Tieghem, were separated and purified to homogeneity. The enzymes, produced in a selective medium, were separated and purified on a column of DEAE‐Sephadex A‐50. The molecular weights of AG‐I and AG‐II were found to be 69, 810 and 89,130 respectively. The two enzymes were glycoproteins and differed in their carbohydrate contents, pH and temperature stabilities and optima for activity. Their activation energies and Km values also varied. AG‐II, had a higher molecular weight, carbohydrate content, increased acid tolerance and was synthesized earlier to AG‐I (when the pH of the medium was acidic). Hg and Ag salts caused partial inhibition of their activities.

Clustering of catalytic nanocompartments for enhancing an extracellular non-native cascade reaction

“…The molecular weight 48 and dimensions of AMG from Aspergillus niger (75Å Â 45Å Â 40Å, PDB code 6YQ7, manually measured using Pymol) indicate that the size of AMG is orders of magnitude smaller than that of polymersomes. Accordingly, FCS measurements did not reveal any signicant shi in the diffusion times if AMG was conjugated to GOX-CNCs (6000 ms for AMG-conjugated CNCs versus 5486 AE 2510 ms for CNCs without AMG).…”

“…To provide one step further in the cascade complexity, we conjugated amyloglucosidase (AMG), an exoenzyme that hydrolyses amylose into small glucose units, 48 to the surface of GOX-nanocompartments. Due to the external location of AMG, thousands of g mol À1 large amylose could be hydrolyzed to glucose that could enter the compartment and serve as substrate for the GOX encapsulated.…”

Glucoamylases: Microbial Sources, Industrial Applications and Molecular Biology ? A Review

“…The two forms of glucoamylase (AG-I and AG-11) isolated from A. niger van Tieghem, however, differed in their carbohydrate content, as well as the pH and temperature stabilities and optima for activity (Ramasesh et al 1982). Their activation energies and K , values also varied and AG-11 had higher carbohydrate content, with an increased acid tolerance.…”

Evidence that cleavage of the precursor enzyme by autocatalysis caused secretion of multiple amylases by Aspergillus niger

“…A. niger used in this study is an industrial strain isolated for glucoamylase production [3] and maintained in this laboratory under accession number CFTRI 1105. A protease‐overproducing mutant of this fungus was obtained after UV irradiation.…”

“…However, multiple amylases have been described from the species of Aspergillus [1]. Aspergillus niger has been reported to produce two forms of glucoamylase [3], α‐amylase [4], starch‐hydrolysing enzyme [5], α‐glucosidase [6] and Taka‐amylase [7]. Despite the above reports, the literature is not clear on the mechanism of multiple amylase production by A. niger .…”