Mode of binding of pyrroloquinoline quinone to apo-glucose dehydrogenase.

Abstract

Whilst in acetic acid bacteria glucose dehydrogenase (EC 1.1.99.a) is abundantly formed in the cytoplasmic membrane, the enzyme was also found more or less in various other microorganisms in which its existence had not been reported previously. Glucose dehydrogenase from Escherichia coli occurred almost completely as the apoenzyme, being freed from pyrroloquinoline quinone (PQQ), a unique prosthetic group of the enzyme. Treatment of the E. coli membrane with EDTA caused a complete loss of the enzyme activity and subsequent addition of exogenous PQQ gave rise to no reactivation of the enzyme unless some magnesium ions were added. The magnesium ions could function by anchoring the PQQ to the apoenzyme.