Elucidation of the region responsible for EDTA tolerance in PQQ glucose dehydrogenases by constructing Escherichia coli and Acinetobacter calcoaceticus chimeric enzymes.

We constructed various chimeric PQQ glucose dehydrogenases (PQQGDHs) from an EDTA-sensitive PQQGDH from Escherichia coli and an EDTA-tolerant PQQGDH from Acinetobacter calcoaceticus by homologous recombination of their structural genes. The EDTA tolerance of the resulting chimeric enzymes was investigated. Our results demonstrated that EDTA tolerance of PQQGDHs can be completely altered by substituting each corresponding region. The EDTA tolerance of A. calcoaceticus PQQGDH is mostly within a region composed of about 90 amino acid residues located between 45 and 56% of the distance from the N-terminal region.