Participation of εADP and εATP in the reactions of oxidative phosphorylation in rat liver mitochondria

Bârzu, Octavian; Kiss, Levente; Bojan, O.; Niac, Gavril; Mantsch, Henry H.

doi:10.1016/0006-291x(76)90206-0

Cited by 12 publications

(8 citation statements)

References 14 publications

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“…They are the N 1 ,N i -etheno (E) nucleotides, E-ADP or E-ATP (56), and the 8-amino-3(j3o-ribo-furanosyl)-imidazo [4][5]quinazoline-5' -nucleotides (lin-benzo ADP and ATP) (57). E-ATP is not transported by the AdN carrier of rat liver mitochondria, but it is hydrolyzed by the exposed FJ of inverted submitochondrial particles, at a rate six times lower than that of ATP (59,60). E-ATP is not transported by the AdN carrier of rat liver mitochondria, but it is hydrolyzed by the exposed FJ of inverted submitochondrial particles, at a rate six times lower than that of ATP (59,60).…”

Section: Modiaed Purine Ringmentioning

confidence: 89%

Chemical Probes of the Mitochondrial Atp Synthesis and Translocation

Vignais¹,

Lunardi²

1985

Annu. Rev. Biochem.

103

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Section: Modiaed Purine Ringmentioning

confidence: 89%

Chemical Probes of the Mitochondrial Atp Synthesis and Translocation

Vignais¹,

Lunardi²

1985

Annu. Rev. Biochem.

103

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“…The rate of respiration stimulation by 8-BrADP is strongly dependent on the Mg2+ concentration in the medium as well as on the 8-BrADP concentration itself (Figure 1). In the absence of exogenous Mg2+, 8-BrADP, similar to the previously investigated nucleotide analogues o'ADP and cADP (Kezdi et al, 1973;Bárzu et al, 1976b), has no effect at all on mitochondrial respiration. However, unlike the situation with o'ADP and eADP, increasing concentrations of 8-BrADP lead to a progressive inhibition of mitochondrial respiration.…”

Section: Resultsmentioning

confidence: 54%

“…While Hohnadel & Cooper (1972) could show that sonicated rat liver mitochondrial membranes are able to make use of other natural or synthetic ATP analogues as acceptors in the mechanism of oxidative phosphorylation, we have shown in previous experiments (Bárzu et al, 1976b) that o'ADP and eADP cannot act as phosphate acceptors in the reactions of oxidative phosphorylation catalyzed by lubrol particles obtained from rat liver mitochondria. Therefore, along with 8-BrADP, we also investigated the above-mentioned analogues in their behavior toward MgATP particles obtained from beef heart mitochondria (Figure 3).…”

Section: Resultsmentioning

confidence: 68%

Enzymic properties of 8-bromoadenine nucleotides

Lascu¹,

Kezdi²,

Goia³

et al. 1979

Biochemistry

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8-Bromoadenine nucleotides were tested as potential substrates and/or inhibitors of mitochondrial processes in intact or disrupted organelles, as substrates of various phosphotransferases, and as allosteric effectors in the reactions catalyzed by phosphofructokinase, isocitrate dehydrogenase, glutamate dehydrogenase, and fructose-1,6-bisphosphatase. 8-BrATP and 8-BrADP are not recognized by the translocase system located in the inner mitochondrial membrane and cannot be used as usbstrates in oxidative phosphorylation and related reactions catalyzed be beef heart submitochondrial membranes. This confirms the high specificity for adenine nucleotides of the mammalian systems involved in energy-yielding and energy-requiring reactions. However, 8-BrATP and 8-BrADP are able to substitute for the natural adenine nucleotides in reactions catalyzed by many phosphotransferases, although their capacity as phosphate donors and acceptors is generally much reduced. On the other hand, in almost all investigated cases, the 8-bromoadenine nucleotides have lost the capability of the natural adenine nucleotides to act as allosteric effectors, indicating that the structural requirements for allosteric activity are more stringent than those for catalytic activity.

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“…In the presence of Mg2+, the phosphorylation of TuDP and dADP by rat liver mitochondria increases significantly (with 35% and 22%, respectively), due to the intervention of the mitochondrial NDP kinase. It is worth mentioning that o'ADP, a nucleotide which neither is translocated nor serves as a substrate in oxidative phosphorylation (Mantsch et al, 1975;Bárzu et al, 1976b) is phosphorylated by rat liver mitochondria in the presence of Mg2+ at a rate of 5.7 nmol min-1 (mg of protein)"1 by coupling the intramitochondrial ADP phosphorylation to the NDP kinase reaction. The phosphorylation of TuDP and dADP in beef heart mitochondria is less intense than in the case of rat liver, either because of a smaller translocation rate or because of a higher specificity for ADP of the heart system of oxidative phosphorylation.…”

Section: Resultsmentioning

confidence: 99%

“…Biochemical Assays. The isolation of rat liver mitochondria, the measurement of mitochondrial respiration, and the exchange of intramitochondrial 14C-labeled adenine nucleotides with externally added nucleotide analogues were performed as described in previous publications (Jebeleanu et al, 1974;Mantsch et al, 1975;Bárzu et al, 1976b). Heavy beef heart mitochondria were prepared as described by Low & Vallin (1963), stored for 2-7 days at -10 °C, and thawed only shortly before use.…”

Section: Methodsmentioning

confidence: 99%

Phosphorylation and hydrolysis of 7-deazaadenine nucleotides by rat liver and beef heart mitochondria

Petrescu¹,

Lascu²,

Goia³

et al. 1982

Biochemistry

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Tubercidin nucleotides [tubercidin 5'-mono-phosphate (TuMP), 5'-diphosphate (TuDP), and 5'-triphosphate (TuTP)] were tested as potential substrates for the mitochondrial phosphotransferases from rat liver and beef heart. TuDP is recognized by the mitochondrial translocase and phosphorylated by the respiratory chain enzymes in both mitochondria and submitochondrial particles from rat liver and beef heart; the low transport rate of the analogue into the matrix space of the intact organelles seems to be not a limiting step in the formation of TuTP. The phosphorylation of TuDP is significantly lower in beef heart mitochondria because of a higher specificity for ADP of the heart oxidative phosphorylation system. On the basis of the kinetic parameters of the partially purified liver mitochondrial adenylate kinase, one can conclude that the liver mitochondria are able to phosphorylate in vivo TuMP at a rate practically equal to the rate of AMP phosphorylation. The liver mitochondrial NDP kinase ensures a further fast phosphorylation of TuDP without the direct involvement of respiratory chain enzymes. In the case of heart mitochondria, two factors limit the rate of TuMP phosphorylation to TuTP: the lower acceptor activity of adenylate kinase with TuMP as compared with AMP and the different localization of heart NDP kinase situated on the inner face of the inner mitochondrial membrane. TuDP and TuTP preserve the ability of the natural nucleotides to interact with the "tight" nucleotide binding sites of isolated or membrane-bound F1. The low hydrolytic rate of TuTP with F1 may be related to the unusual flexibility of the glycosyl bond of tubercidin nucleotides in aqueous solution, with a high accessibility to syn conformation.

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Participation of εADP and εATP in the reactions of oxidative phosphorylation in rat liver mitochondria

Cited by 12 publications

References 14 publications

Chemical Probes of the Mitochondrial Atp Synthesis and Translocation

Chemical Probes of the Mitochondrial Atp Synthesis and Translocation

Enzymic properties of 8-bromoadenine nucleotides

Phosphorylation and hydrolysis of 7-deazaadenine nucleotides by rat liver and beef heart mitochondria

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