The Pyridine-nucleotide Transhydrogenase of Salmonella typhimurium

Abstract

SUMMARYEnergy-dependent and energy-independent transhydrogenase activities in the membrane particle fraction from Salmonella typhimurium were less markedly repressed by amino acids than in Escherichia coli. Energy-dependent transhydrogenation of NADP+ by NADH was driven either by energy from NADH oxidation through the respiratory chain, or from ATP, GTP or ITP but not by CTP, UTP, ADP and adenosine monophosphates. Adenosine monophosphates had little effect on ATP-driven and energy-independent reactions but $-AMP and 3',5'-AMP, like cyanide and sulphide, inhibited the aerobic-driven reaction via an inhibitory effect on the respiratory chain of the organism. Dicyclohexylcarbodi-imide and phosphate inhibited the use of ATP as an energy donor, while carbonyl cyanide-rn-chlorophenylhydrazone discharged the energized state required for energy-dependent transhydrogenation. Washing removed proteins needed for both energy-dependent activities but not for the energy-independent reaction. Re-addition of the 'coupling factor' restored the lost activities fully. Coupling factor preparations from this organism and from E. coli were interchangeable.

Salmonella typhimurium HfrA, a mutant in which adenosine triphosphate can drive amino acid transport but not energy-dependent nicotinamide nucleotide transhydrogenation

“…1K1 A tELI k r--inhibits at the level of the cytochrome oxidases in S. typhimurium (Singh & Bragg, 1974). Therefore these results are consistent with the hypothesis (Klein & Boyer, 1972;Parnes & Boos, 1973) that transport under aerobic conditions was energized primarily by substrate oxidation through the respiratory chain, whereas ATP was the prime energy donor under anaerobic conditions.…”

“…ATPase activity was determined in the presencw of 5mM-CaCl2. Energy-independent transhydrogenation of 3-acetylpyridine-NAD+ by NADPH was assayed as described by Singh & Bragg (1974). Energy-linked reduction of NAD+ by succinate, DL-a-glycerophosphate and D-lactate was measured by using membrane particles prepared from cells grown on the medium described by Poole & Haddock (1974) with 0.5 % glycerol as the carbon source.…”