Electron transport chain and energy transduction in Paracoccus denitrificans under autotrophic growth conditions

Cells of Paracoccus denitrificans grown autotrophically with H2 as energy source contained a branched respiratory chain. The presence of two terminal oxidases was indicated by two cyanide sensitive sites (Ki=10-5 M and Ki=10-3 M). While oxidation of NADH and succinate apparently proceeded via both electron pathways as shown by the inhibition of respiration with cyanide and Antimycin A, oxidation of H2 involved only the terminal oxidase which was less sensitive to KCN. Oxidation of H2 was not inhibited by rotenone, and sensitive to only relatively high concentrations of Antimycin A (50 nmol/mg).