GLUCOAMYLASES ENCODED BY VARIANT SACCHAROMYCOPSIS-FIBULIGERA GENES - STRUCTURE AND PROPERTIES

The genes of two variant glucoamylases (GLA1 and GLU1) of Saccharomyco psis fibuligera were expressed in Saccharomyces cerevisiae, and bioche mical properties of the secreted enzymes were compared. It was found t hat three amino acid alterations in the signal peptide and N-terminal regions of the variants had no effect on the levels of the secreted en zymes. Amino acid alterations in the C-terminal region of the mature p roteins influenced their specific activity, substrate specificity, as well as temperature and pH optima. Because of the glycosylation hetero geneity, the glucoamylases of each gene variant were isolated and puri fied in two forms (A and B), which were essentially similar in catalyt ic and physicochemical properties but differed in their thermal stabil ity and ability to renaturate after thermal denaturation.