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Keywords:

  • Carbon monoxide dehydrogenase;
  • intracellular location;
  • molybdenum cofactor;
  • bactopterin;
  • CO-insensitive respiration;
  • reverse electron transfer

Abstract The use of CO as a growth substrate by aerobic CO-oxidizing (carboxydotrophic) bacteria requires some features not obvious in other bacteria. These are the presence of the enzyme CO dehydrogenase, a branched respiratory chain with an alternative CO-insensitive terminal oxidase (cytochrome b653) and formation of reduced pyridine nucleotides by a pmf-driven reversed electron transfer. Immunocytochemical localization studies revealed that CO dehydrogenase is attached to the inner aspect of the cytoplasmic membrane of Pseudomonas carboxydovorans. The enzyme is a molybdo iron-sulfur flavoprotein containing bactopterin as the organic portion of the molybdenum cofactor. Recent findings suggest that this novel pterin is universal to eubacterial molybdenum enzymes, whereas molybdopterin is universal to eukaryotic molybdoenzymes.