Rhizopus Raw-Starch-Degrading Glucoamylase: Its Cloning and Expression in Yeast

抄録

A glucoamylase gene has been cloned from a Rhizopus genomic DNA library using synthetic oligonucleotides corresponding to the amino acid sequence of the glucoamylase. Since this glucoamylase gene was not expressed in yeast cells, we have cloned a glucoamylase gene from a cDNA library prepared from Rhizopus mRNA. Sequence analysis of both glucoamylase genes revealed that the genomic gene contained 4 intervening sequences and the cDNA gene lacked 145 nucleotides corresponding to the N-terminal region. The glucoamylase consists of 604 amino acids including a putative signal peptide and its molecular weight was calculated to be 65, 000. The glucoamylase gene to be expressed in yeast cells was constructed by recombination of both genes. The yeast cells containing this constructed glucoamylase gene secreted the glucoamylase into the culture fluid and grew at almost the normal rate on a medium containing starch as the sole carbon source.