Expression of an Aspergillus glucoamylase gene in yeast

The extracellular glucoamylase from Aspergillus awamori is an enzyme of choice in commercial saccharification processes. However, no expression of glucoamylase protein or mRNA was observed when Yep vectors carrying the glucoamylase structural gene and considerable 5'- and 3'-flanking sequence were introduced into strains of yeast. The lack of expression results both from the inability of yeast to recognize the Aspergillus promoter and from failure of yeast to properly excise the Aspergillus introns. In order to express Aspergillus glucoamylase in yeast, the authors used oligonucleotide directed mutagenesis techniques and partial cDNA clones to delete the four introns and introduce a yeast promoter, EN01 , at the 5'-end of the gene.