Energy-linked incorporation of citrate into rat liver mitochondria

Max, Stephen R.; Purvis, John L.

doi:10.1016/0006-291x(65)90526-7

Cited by 38 publications

(12 citation statements)

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“…The inner mitochondrial membrane is readily permeable only to uncharged molecules of low molecular weight, but contains a number of specific carrier systenms for substrate anions (Chappell & Haarhoff, 1967;Robinson & Chappell, 1967a;Azzi, Chappell & Robinson, 1967;de Haan & Tager, 1968). Harris, van Dam & Pressman (1967c,d) and Quagliariello & Palmieri (1968) confirmed and extended the earlier observations of Max & Purvis (1965) and Gamble (1965) that intact mitochondria can accumulate high concentrations of substrate anions in an energy-dependent reaction. The accumulation of substrate anions required the presence of cations that could be actively transported, such as Ca2+, or K+ in the *Present address: Department of Biochemistry, Monash University, Clayton, Vic., Australia.…”

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confidence: 62%

Factors affecting the translocation of oxaloacetate and l-malate into rat liver mitochondria

Haslam

Griffiths

1968

Biochemical Journal

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1. The rates of translocation of oxaloacetate and l-malate into rat liver mitochondria were measured by a direct spectrophotometric assay. 2. Penetration obeyed Michaelis-Menten kinetics, and apparent K(m) values were 40mum for oxaloacetate and 0.13mm for l-malate. 3. Arrhenius plots of the temperature-dependence of rates of penetration gave activation energies of +10kcal./mole for oxaloacetate and +8kcal./mole for l-malate. 4. The translocation of both oxaloacetate and l-malate was competitively inhibited by d-malate, succinate, malonate, meso-tartrate, maleate and citraconate. The K(i) values of these inhibitors were similar for the penetration of both oxaloacetate and l-malate. 5. Rates of penetration were stimulated by NNN'N'-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate under aerobic conditions or by ATP under anaerobic conditions. 6. The energy-dependent stimulation of translocation was abolished by uncouplers of oxidative phosphorylation. Oligomycin A, aurovertin, octyl-guanidine and atractyloside prevented the stimulation by ATP, but did not inhibit the stimulation by NNN'N'-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate. 7. Mitochondria prepared in the presence of ethylene-dioxybis(ethyleneamino)tetra-acetic acid did not exhibit the energy-dependent translocation, but this could be restored by the addition of 50mum-calcium chloride. 8. Valinomycin or gramicidin plus potassium chloride enhanced the energy-dependent translocation of oxaloacetate and l-malate. 9. Addition of oxaloacetate stimulated the adenosine triphosphatase activity of the mitochondria, and the ratio of ;extra' oxaloacetate translocation to ;extra' adenosine triphosphatase activity was 1.6:1. 10. Possible mechanisms for the energy-dependent entry of oxaloacetate and l-malate into mitochondria are discussed in relation to the above results.

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confidence: 62%

Factors affecting the translocation of oxaloacetate and l-malate into rat liver mitochondria

Haslam

Griffiths

1968

Biochemical Journal

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“…There are two mechanisms by which anions can be accumulated in mitochondria; one is a process of anion exchange, which when endogenous reserves are depleted may become energy-dependent (Max & Purvis, 1965;Harris & Manger, 1968). The other process involves simultaneous gain of K+ and anion; this is easiest to demonstrate when K+ uptake is induced with an antibiotic such as valinomycin (e.g., see Fig.…”

Section: Discussionmentioning

confidence: 99%

Intramitochondrial substrate concentration as a factor controlling metabolism. The role of interanion competition

Harris

Manger

1968

Biochemical Journal

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1. The concentration-dependence of the intramitochondrial accumulation of l-malate and succinate was measured and expressed in the form of adsorption isotherms. The accumulation, however, may arise because of an internal positive potential. 2. The competition for accumulation offered by some other anions, including phosphate, was measured and is expressed conventionally by additional terms in the adsorption equation. 3. The interactions between anions were also studied when one was acting as oxidized substrate. 4. In some examples there is a parallel between the effects of an added anion on both accumulation and oxidation; in other cases chemical participation of the added substance in metabolism is presumed to remove the correlation. 5. It is suggested that by combining kinetic data on penetration with stoicheiometric data on accumulation and specific reaction rates it may be possible to account for the rates of respiration obtained with intact mitochondria. 6. It is possible to show that there is a certain phosphate/substrate ratio for maximum phosphorylation rate with some substrates. This is to be expected when phosphate and substrate compete for accumulation.

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“…It was shown that about 32% of the citrate synthesized in mitochondria passes into the extramitochondrial space (Buffa et al, 1972). Evidence is available for citrate transport and/or diffusion from mitochondria to cytosol in liver and heart, with subsequent utilization by extramitochondrial aconitase (which is almost unaffected by FA intoxication) and NADP-dependent isocitrate dehydrogenase (Max and Purvis, 1965). These processes should be considered adaptive and positive, since they serve for reducing oxygen uptake: the NADPH formed needs not to be oxidized in the respiratory chain and can take part in glutathione-dependent defluorinating reactions.…”

Section: Are There Alternative Strategies To Development Of Effectivementioning

confidence: 98%

Toxicology of fluoroacetate: a review, with possible directions for therapy research

2006

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Fluoroacetate (FA; CH2FCOOR) is highly toxic towards humans and other mammals through inhibition of the enzyme aconitase in the tricarboxylic acid cycle, caused by 'lethal synthesis' of an isomer of fluorocitrate (FC). FA is found in a range of plant species and their ingestion can cause the death of ruminant animals. Some fluorinated compounds -- used as anticancer agents, narcotic analgesics, pesticides or industrial chemicals -- metabolize to FA as intermediate products. The chemical characteristics of FA and the clinical signs of intoxication warrant the re-evaluation of the toxic danger of FA and renewed efforts in the search for effective therapeutic means. Antidotal therapy for FA intoxication has been aimed at preventing fluorocitrate synthesis and aconitase blockade in mitochondria, and at providing citrate outflow from this organelle. Despite a greatly improved understanding of the biochemical mechanism of FA toxicity, ethanol, if taken immediately after the poisoning, has been the most acceptable antidote for the past six decades. This review deals with the clinical signs and physiological and biochemical mechanisms of FA intoxication to provide an explanation of why, even after decades of investigation, has no effective therapy to FA intoxication been elaborated. An apparent lack of integrated toxicological studies is viewed as a limiter of progress in this regard. Two principal ways of developing effective therapies for FA intoxication are considered. Firstly, competitive inhibition of FA interaction with CoA and of FC interaction with aconitase. Secondly, channeling the alternative metabolic pathways by orienting the fate of citrate via cytosolic aconitase, and by maintaining the flux of reducing equivalents into the TCA cycle via glutamate dehydrogenase.

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Energy-linked incorporation of citrate into rat liver mitochondria

Cited by 38 publications

References 8 publications

Factors affecting the translocation of oxaloacetate and l-malate into rat liver mitochondria

Factors affecting the translocation of oxaloacetate and l-malate into rat liver mitochondria

Intramitochondrial substrate concentration as a factor controlling metabolism. The role of interanion competition

Toxicology of fluoroacetate: a review, with possible directions for therapy research

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