The Glucoamylase cDNA from Aspergillus oryzae: Its Cloning, Nucleotide Sequence, and Expression in Saccharomyces cerevisiae

A cDNA for Aspergillus oryzae glucoamylase was cloned, using oligodeoxyribonucleotide probes derived from amino sequences of peptide fragments of the enzyme. The glucoamylase cDNA, when introduced into Saccharomyces cerevisiae, directed the secretion of active glucoamylase into the culture medium. The complete nucleotide sequence of the cDNA contained an open reading frame encoding 612 amino acid residues. Comparative studies with other fungal glucoamylases showed homologies of 67% with A. niger and 30% with Rhizopus oryzae of the deduced amino acid sequences. In the five conserved regions reported in other fungal glucoamylases, the levels of homologies between those regions of A. oryzae and A. niger enzymes were much higher (78–94%). A. oryzae glucoamylase contained no peptide region abundant in threonine and serine residue (TS-region), like that proposed to adsorb onto raw starch in A. awamori var. kawachii glucoamylase.