Quinoprotein D-glucose dehydrogenase in Acinetobacter calcoaceticus LMD 79.41: the membrane-bound enzyme is distinct from the soluble enzyme

Abstract Acinetobacter calcoaceticus is known to contain soluble and membrane-bound quinoprotein D -glucose dehydrogenases while other oxidative bacteria such as Pseudomonas or Gluconobacter contain only membrane-bound enzyme. The two different forms were believed to be the same enzyme or interconvertible. Present results show that the two different forms of glucose dehydrogenase are distinct from each other in their enzymatic and immunological properties as well as in their molecular size. The two enzyme forms were separated after French press-disruption by repeated ultracentrifugation. The soluble and membrane-bound enzymes showed different properties including substrate specificity, kinetics for glucose, and reactivity for ubiquinone-homologues. Importantly, the distinct properties of both enzymes could be retained even after partial purification of the soluble enzyme and solubilization of the membrane-bound enzyme with Triton X-100. Furthermore, the two forms could be distinguished immunochemically; the membrane-bound form contains a polypeptide of 83 kDa cross-reactive with antibody raised against Pseudomonas enzyme while the soluble enzyme may be a 55 kDa peptide which is not cross-reactive with the antibody.