The purification and properties of glucoamylase (α-l,4-glucan glucohydrolase, EC 220.127.116.11) from different fungal sources have been compared. The studies on the conformation and activity of the native enzyme at a function of pH, temperature, substrate concentration and the effect of denaturants and on the role of carbohydrate moiety on structure and stability have been reviewed. The chemical modification of the active centre, binding kinetics of the substrate and active site and the mechanism of action have been summarized. They differ in their fine structure as revealed by their near ultra-violet circular dichroism spectra and contain 30–35 % α-helix, 24–36 %Β-structure and the rest aperiodic structure. The activity of the enzyme is very sensitive to the environment around aromatic aminoacid residues.
The glucoamylases are glycoprotein in nature, differ in their content and nature of carbohydrate from different sources. The carbohydrate moiety plays an important role in stabilising the native conformation of the enzyme and is not involved in activity and antigenecity.
At the active site of the enzyme, two tryptophan and two carboxyl (glutamate or aspartate) groups are present. It is likely that the histidine and tyrosine residues which are present away from the active site are involved in binding of the substrate. There seems to be seven subsites which are involved in binding of the substrate and the catalytic site is situated in between 1 and 2 subsites. In breaking of α-1,4-, α-1,3-, and α-l,6-bonds only one active centre is involved.
Studies on the immobilization of either glucoamylase alone or as a part of a multienzyme system have been reviewed briefly
Volume 48, 2023
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