Attachment of CO dehydrogenase to the cytoplasmic membrane is limiting the respiratory rate of Pseudomonas carboxydovorans

Abstract Cells of Pseudomonas carboxydovorans from the exponential growth phase revealed the major portion (87%) of CO dehydrogenase attached to the inner aspect of the cytoplasmic membrane. In stationary cells only about half of the total amount of the enzyme remained membrane-bound, and a drop of the CO-oxidizing activity with O₂ was observed. The CO-oxidizing activity with the unphysiological electron acceptor methylene blue, which does not need any contact of the enzyme with the membrane, always exceeded that with O₂. Measurements of respiration rates of extracts with different electron donors in addition to CO suggested that the electron transport chain is not rate-limiting. It is concluded that the electron flow from CO to O₂ in intact cells of P. carboxydovorans is controlled by the amount of CO dehydrogenase attached to a membrane-bound electron acceptor.