Production of the Maltopentaose-Forming Enzyme and Its Application

The gene coding for the maltopentaose (G5)-forming enzyme of Pseudonaonas sp. KO-8940 was cloned into Escherichia coli and its nucleotides sequenced. It was found to have a long open reading frame composed of 1842 by that encoded 614 amino acid residues for a secretory precursor polypeptide including the typical signal sequence with an NH2-terminal. In the deduced primary structure of this enzyme, a high degree of homology to four regions conserved by many α-amylases was found, and the COOH-terminal portion of this enzyme showed high homology with other raw starch digesting amylases. The G5-forming enzyme was produced in large amount (52.7 IU/ml, 0.1 g/l) in E. coli under the tac promoter. This result showed that the G5-forming enzyme can be produced in E. coli carrying this enzyme gene expression vector at levels up to 6 times greater than the native production system found in P, sp. KO-8940.