THERMOSTABLE CHIMERIC PQQ GLUCOSE-DEHYDROGENASE

The thermal stability of PQQ glucose dehydrogenases (PQQGDHs) which we re chimeras with more than 95% made up of the N-terminal region of Esc herichia coli PQQGDH and the rest made up of the C-terminal region of Acinetobacter calcoaceticus PQQGDH was investigated, Among the chimeri c PQQGDHs, E97A3 (E. coli 97% and A. calcoaceticus 3%) and E95A5,were found to possess higher thermal stability than parental E. coli PQQGDH , Further detailed characterization of the thermal stability was carri ed out, focusing on E97A3. E97A3 showed a more than 3-fold and 12-fold increase in half life time at 40 degrees C, compared with the PQQGDHs of E. coli and A. calcoaceticus, respectively, Using transition state theory, the increase in the free energy of inactivation observed in E 97A3 was compared with those of the E. coli and A. calcoaceticus paren tal enzymes. The region responsible for this stabilization was also di scussed.