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) f rom an EDTA-sensitive PQQGDH from Escherichia coli and an EDTA-toleran t PQQGDH from Acinetobacter calcoaceticus by homologous recombination of their structural genes. The EDTA tolerance of the resulting chimeri c enzymes was investigated. Our results demonstrated that EDTA toleran ce of PQQGDHs can be completely altered by substituting each correspon ding region. The EDTA tolerance of A. calcoaceticus PQQGDH is mostly w ithin a region composed of about 90 amino acid residues located betwee n 45 and 56 % of the distance from the N-terminal region. (C) 1995 Aca demic Press, Inc.