PQQ-Dependent Production of Gluconic Acid by Acinetobacter, Agrobacterium and Rhizobium Species

SUMMARY: Acinetobacter Iwoffi, Azotobacter vinelandii, Agrobacterium and Rhizobium species contain quinoprotein glucose dehydrogenase apoenzyme (EC 1.1.99.17). Addition to whole cells of pyrrolo-quinoline quinone (PQQ), the prosthetic group of this enzyme, resulted in the production of gluconic acid from glucose. The in vivo reconstitution of apo-glucose dehydrogenase with PQQ was dependent on the presence of Ca2+ or Mg2+. Optimal conditions for reconstitution allowed maximal glucose dehydrogenase activity in the presence of 1–10 nmol PQQ 1−1. Synthesis of the apoenzyme of glucose dehydrogenase was not dependent on glucose in the growth media. The physiological significance of the synthesis of apo-glucose dehydrogenase, as found in a variety of bacteria, is discussed.