Generation of Reducing Power in Chemosynthesis III. Energy-Linked Reduction of Pyridine Nucleotides in Thiobacillus novellus

Aleem, M. I. H. (Research Institute for Advanced Studies, Baltimore, Md.). Generation of reducing power in chemosynthesis. III. Energy-linked reduction of pyridine nucleotides inThiobacillus novellus . J. Bacteriol.91: 729–736. 1966.—Cell-free extracts fromThiobacillus novellus . catalyzed an adenosine triphosphate (ATP)-dependent reduction of pyridine nucleotides anaerobically, or aerobically when the respiratory chain was inhibited by azide. The exogenous electron donor employed for the reduction of nicotinamide adenine dinucleotide or nicotinamide adenine dinucleotide phosphate (NADP) was thiosulfate, formate, or mammalian ferrocytochromec . In the latter case, the oxidation of ferrocytochromec was observed with the concomitant reduction of the pyridine nucleotide. Values calculated for the molar ratios of ATP utilized-NADP reduced and of cytochromec oxidized-NADP reduced were 1:1 and 2:1, respectively. The energy-dependent reduction of the pyridine nucleotides was inhibited by Atabrine or amytal and by low concentrations of the uncouplers of oxidative phosphorylation such as 2,4-dinitrophenol and carbonyl cyanidem -chlorophenyl hydrazone. Evidence is presented showing that the reduced pyridine nucleotides are essential for providing the reducing power for the energy-dependent reduction of carbon dioxide inT. novellus .