Stereochemistry of hydrogen-transfer in the energy-linked pyridine nucleotide transhydrogenase and related reactions

Lee, Chuan-Pu; Simard‐Duquesne, N.; Ernster, Lars; Hoberman, Henry D.

doi:10.1016/s0926-6593(65)80226-0

Cited by 116 publications

(47 citation statements)

References 29 publications

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“…I n the presence of an energy supply, the nicotinamide nucleotide transhydrogenase reaction may be visualized to involve an energy-linked activation of the enzyme, according to the equation TH + I N X +TH* + I + X (10) which thus will promote reaction (9) from left to right and inhibit it from right to left. The overall energy-linked nicotinamide nucleotide transhydrogenase system will thus operate as a cyclic process, TH* + NADH + NADP+ + TH + NAD+ + NADPH I n earlier work [4,5,9] it was suggested that the energy-linked transhydrogenase reaction may involve energized forms of nicotinamide nucleotides. The present results suggest an alternative mechanism, involving an energy-linked alteration of the transhydrogenase molecule itself.…”

Section: Discussionmentioning

confidence: 99%

“…Deproteinizations and measurements of the radioactivity were performed as described by Lee et al [9].…”

Section: Methodsmentioning

confidence: 99%

“…I n order to investigate this possibility it was of interest to determine the rate of the reverse nonenergy linked reaction during steady state and to compare it with the corresponding rate in the absence of an energy supply (Fig.6). The measurements were based on the use of [4-3H]NAD+, which is reduced in the course of the transhydrogenase reaction to [4B-3H]NADH [9]. The latter then rapidly exchanges its 4B hydrogen atom with that of H,O via Eur.…”

Section: Pig 1 a T'he Forward (M--)mentioning

confidence: 99%

“…The reaction mixture consisted of 0.1 M Tris-acetate buffer, 8 the respiratory chain-linked NADH dehydrogenase reaction (cf. [9,13] Fig.6B shows data from the same experiment, performed in the presence of an energy supply (succinate). As expected, the energy supply prevented the nicotinamide nucleotides from equilibrating according to the nonenergy-linked reaction, and these reached steady state after about 2min.…”

Section: K' (= "Ad+] [Nadph]i[nadh]/[nadp+]) As a Function Of The Ratmentioning

confidence: 99%

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Factors Governing the Kinetics and Steady State of the Mitochondrial Nicotinamide Nucleotide Transhydrogenase System

Rydström¹,

Cruz²,

Ernster³

1970

European Journal of Biochemistry

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The mitochondria1 nicotinamide nucleotide transhydrogenase catalyzes a rapid reduction of NAD+ by NADPH as compared to the reduction of NADP+ by NADH. By Evidence is presented that the final extent of the overall energy-linked transhydrogenase reaction is strikingly dependent on the ratio of the initial rates of the energy-linked reduction of NADP+ by NADH and the nonenergy-linked reduction of NAD+ by NADPH. Thus, the final extent of the transhydrogenase reaction in the presence of an energy source can by explained in terms of a steady state rather than a n equilibrium. The possibility of a n energy-linked conformational change of transhydrogenase, involving a conversion of the enzyme from an inactive to an active state, is considered.Submitochondrial particles catalyze two types of nicotinamide nucleotide transhydrogenase reaction : a "nonenergy-linked" transhydrogenase reaction, No explanation for this discrepancy has so far been provided. By assuming pseudo first-order kinetics for the nonenergy-linked transhydrogenase reaction, it will be demonstrated in this paper that the initial rates of the forward and backward reactions are influenced by the prevailing concentrations of nicotinamide nucleotides .Enzymes. Alcohol dehydrogenase (EC 1.1.1.1) The energy-linked transhydrogenase reaction exhibits a left-to-right initial velocity greatly exceeding that of the corresponding nonenergy-linked reaction, and its apparent equilibrium constant It therefore appeared conceivable that the energy-linked transhydrogenase reaction per se is practically irreversible and that K is determined by the steady state resulting from the relative rates of this reaction and the right-to-left course of nonenergy-linked transhydrogenase reaction. Variation of the individual rates of the two reactions should thus result in changes of the magnitude of K'. The data reported in this paper show that this indeed is the case.

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Section: Discussionmentioning

confidence: 99%

“…Deproteinizations and measurements of the radioactivity were performed as described by Lee et al [9].…”

Section: Methodsmentioning

confidence: 99%

Section: Pig 1 a T'he Forward (M--)mentioning

confidence: 99%

Section: K' (= "Ad+] [Nadph]i[nadh]/[nadp+]) As a Function Of The Ratmentioning

confidence: 99%

See 2 more Smart Citations

Factors Governing the Kinetics and Steady State of the Mitochondrial Nicotinamide Nucleotide Transhydrogenase System

Rydström¹,

Cruz²,

Ernster³

1970

European Journal of Biochemistry

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“…The transhydrogenation reaction in this direction does not require an energy source. Studies with mitochondria (Kawasaki, Satoh & Kaplan, 1964;Lee, Simard-Duquesne, Ernster & Hoberman, 1965) suggest that the same enzyme is involved in both the energy-independent and the energy-dependent transhydrogenase reactions. The transhydrogenasel system would thus appear to be ideal for studies of the formation and properties of the energized state.…”

Section: Introductionmentioning

confidence: 99%

The Pyridine-nucleotide Transhydrogenase of Salmonella typhimurium

Singh

Bragg

1974

Journal of General Microbiology

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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.

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