Electrochemical measurements of glucose dehydrogenase activity exhibited by Escherichia coli cells;: effects of the additions of pyrroloquinoline quinone, magnesium or calcium ions and ethylenediaminetetraacetic acid

An electrode modified with immobilized Escherichia coli K12 cells produces a steady-state catalytic current originating from the glucose dehydrogenase activity (GDH) of the bacterial cells. Thus, the catalytic current provides a convenient means of measuring the bacterial GDH activity. E. coli K12 cells cultivated under ordinary conditions exhibit a GDH activity, the magnitude of which is about 15% of the full activity attained in the presence of pyrroloquinoline quinone (PQQ) and magnesium ions. The E. coli K12 cells mostly lose the full GDH activity when treated with ethylenediaminetetraacetic acid, and restore the activity by the additions of PQQ and magnesium or calcium ions. The rate and degree of the restoration of GDH activity strongly depend on the concentrations of PQQ and the divalent cations. The concentration dependence of the bacterial GDH activity is similar to that of the catalytic activity of purified apo-GDH except that the bacterial GDH activity is fully restored by calcium ion as well as magnesium ion, while catalytic activity of apo-GDH is only partially restored by calcium ion. (C) 1998 Elsevier Science S.A.. All rights reserved.