Abstract
For construction of starch-fermentable yeasts which are practically useful for ethanol production from raw starch, we have made some attempts to isolate the secretive glucoamylase-genes from microorganisms. Recently, we achieved the molecular cloning of a glucoamylase-producing gene from the cells of Saccharomyces diastaticus. The isolated gene included 2764 bases encoding 778 amino acid residues, and it was found that the gene in vector-plasmid is expressible in both Saccharomyces cerevisiae and Schizosaccharomyces pombe to give an extracellular glycoamylase. Molecular size of peptidyl part of the purified secretive-glucoamylase was calculated to be approximately 44.5 kilodalton (kd) consisting of 41-kd large and 3.4-kd small subunits, however, an expected molecular-size of the peptidyl part from the gene structure is 80 or more kilo-dalton. The isolated mRNA from the gene donor yeast had a molecular weight corresponding to approximately 2600 bases. Thus, maturation of the enzyme might take place at posttranslational level.
