Protein Engineering of Glucoamylase to Improve Industrial Performance — A Review

Glucoamylase is produced in higher tonnage than almost any other industrial enzyme. However, glucoamylase would be even more useful if it were more thermostable and selective in producing glucose. Extensive work to improve these properties has been conducted by site-directed mutagenesis of selected amino acid residues. Combining favorable mutations has decreased the ability of the enzyme to produce isomaltose, the main byproduct, in the glucoamylase-catalyzed production of glucose by almost half, has increased enzyme thermostability fourfold, and has increased enzyme activity by 15 %. In addition, others have successfully improved catalytic efficiencies for maltose hydrolysis over isomaltose hydrolysis by mutations of glucoamylase. This article will review the improvements that have been made in glucoamylase industrial properties by protein engineering.