Improving operating performance of glucoamylase by mutagenesis.

The potential operating temperature of Aspergillus awamori glucoamylase has been increased by several thermostable mutations that reduce irreversible thermoinactivation. Other mutations have been isolated that increase selectivity of alpha-1,4 over alpha-1,6 glycosidic bonds, resulting in fewer alpha-1,6 linked reversion products, thus increasing glucose yield. Interestingly, many thermostable mutations also increase selectivity and yields, suggesting that enzyme flexibility plays a role in accommodating unwanted bulky alpha-1,6 bonds in the active site.