Electron Transport and Coupled Energy Generation in Pseudomonas saccharophila

Abstract

The respiratory chain system of heterotrophically grown Pseudomonas saccharophila contained cytochromes of the b, c, a, and o types and also the NADH and succinate oxidase enzyme systems. Cell-free extracts catalyzed phosphorylation coupled to the oxidation of NADH, succinate, and ascorbate (plus cytochrome c). The P/O ratios were in the range of 1.00 for generated NADH, 0.29 for added NADH, 0.50 for succinate, and 0.25 for ascorbate (plus cytochrome c).The oxidative phosphorylation was uncoupled by 2,4-dinitrophenol, 2,6-dibromophenol, pentachlorophenol, m-chlorocarbonyl cyanide phenylhydrazone, and dicumarol without any inhibition of oxygen consumption. Phosphorylation coupled to NADH oxidation was completely inhibited by the flavoprotein inhibitors such as rotenone, amytal, and atabrine; these inhibitors had no effect, however, on the ATP synthesis associated with succinate oxidation. Antimycin A or 2-n-nonyl-4-hydroxyquinoline-N-oxide as well as cyanide or azide at low concentrations completely inhibited the phosphate esterification coupled to the oxidation of NADH or succinate, but had little or no effect on the oxygen consumption. Relatively higher concentrations of oligomycin were required for a complete inhibition of the electron-transport-linked ATP formation.