Mode of Binding of Pyrroloquinoline Quinone to Glucose Dehydrogenase from Acinetobacter Calcoaceticus

Abstract

In a number of Gram-negative bacteria a quinoprotein glucose deydrogenase is found, which will loose its prosthetic group, when dialysed against buffer containing EDTA. The apoform of the enzyme can be converted to active holoenzyme by pyrroloquinoline quinone (PQQ) in the presence of Mg²⁺ or Ca²⁺ ions. In contrast the quinoprotein glucose dehydrogenase from Gluconobacter suboxidans (Ameyama et al., 1981) and from Acinetobacter calcoaceticus (Dokter et al., 1986; Geiger and Görisch, 1986) are not inactivated by dialysis against EDTA-containing buffers. However glucose dehydrogenase from A. calcoaceticus is reversibly inactivated by heat treatment, and restoration of active enzyme depends on the presence of PQQ and Ca²⁺ ions.