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PubMed1968

Biochemical effects of the hypoglycaemic compound pent-4-enoic acid and related non-hypoglycaemic fatty acids. Oxidative phosphorylation and mitochondrial oxidation of pyruvate, 3-hydroxybutyrate and tricarboxylic acid-cycle intermediates.

1. The effects of the hypoglycaemic compound pent-4-enoic acid, and of four structurally related non-hypoglycaemic compounds (pent-2-enoic acid, pentanoic acid, cyclopropanecarboxylic acid and cyclobutanecarboxylic acid), on several reactions in rat liver mitochondria were determined. 2. The use of manometric techniques for measurements of oxidations and of phosphorylation is critically discussed. 3. Pent-4-enoic acid and pentanoic acid uncoupled oxidative phosphorylation at low concentrations, but usually by not more than about 50%. 4. All the compounds, except cyclobutanecarboxylic acid, strongly inhibited the oxidation of pyruvate and 2-oxoglutarate, but the oxidations of succinate, citrate and 3-hydroxybutyrate were not strongly inhibited. 5. All the compounds, except cyclobutanecarboxylic acid, inhibited decarboxylation of [1-(14)C]pyruvate with ferricyanide as electron acceptor. 6. All the compounds, except pent-2-enoic acid, caused mitochondrial swelling after a time-lag.

Animals↗
PubMed2003

Acceleration of glycolysis in the presence of the non-phosphorylating and the oxidized phosphorylating glyceraldehyde-3-phosphate dehydrogenases.

Mild oxidation of glyceraldehyde-3-phosphate dehydrogenase in the presence of hydrogen peroxide leads to oxidation of some of the active site cysteine residues to sulfenic acid derivatives, resulting in the induction of acylphosphatase activity. The reduced active sites of the enzyme retain the ability to oxidize glyceraldehyde-3-phosphate yielding 1,3-diphosphoglycerate, while the oxidized active sites catalyze irreversible cleavage of 1,3-diphosphoglycerate. It was assumed that the oxidation of glyceraldehyde-3-phosphate dehydrogenase by different physiological oxidants must accelerate glycolysis due to uncoupling of the reactions of oxidation and phosphorylation. It was shown that the addition of hydrogen peroxide to the mixture of glycolytic enzymes or to the muscle extract increased production of lactate, decreasing the yield of ATP. A similar effect was observed in the presence of non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase catalyzing irreversible oxidation of glyceraldehyde-3-phosphate into 3-phosphoglycerate. A role of glyceraldehyde-3-phosphate dehydrogenase in regulation of glycolysis is discussed.

Adenosine Triphosphate↗
PubMed2025

Structural diversity and evolutionary constraints of oxidative phosphorylation.

The oxidative phosphorylation (OxPhos) system is central to metabolism. The more than 90 structural subunits are encoded by different chromosome categories (autosomal, X, and mtDNA). The system is envisioned as an invariant structure between cells and individuals. However, a comprehensive analysis of the 1,000 Genomes Project data reveals unexpected genetic intra-individual variability resulting from the heterozygosity of diploid autosomal genes, while diversity at the population level is generated by variability in mtDNA. We characterized the different levels of structural constriction at evolutionary and population levels for all OxPhos protein residues. To support this analysis, we developed ConScore, a conservation-based predictor of variant impact within OxPhos proteins (area under the receiver operating characteristic curve [ROC-AUC] = 0.97; area under the precision-recall curve [PR-AUC] = 0.94). Notably, for the nuclear-encoded subunits, we found mechanisms limiting individual variability as allelic imbalance or homozygosity bias. Integrating structural, functional, and genetic data, we highlight the significance of each OxPhos protein position, expanding insights into its role in speciation and disease.

Oxidative Phosphorylation↗
PubMed1989

Slip and leak in mitochondrial oxidative phosphorylation.

During oxidative phosphorylation by mammalian mitochondria part of the free energy stored in reduced substrates is dissipated and energy is released as heat. Here I review the mechanisms and the physiological significance of this phenomenon.

Adenosine Triphosphate↗
PubMed1994

Factors affecting the rate and energetics of mitochondrial oxidative phosphorylation.

Mitochondrial oxidative phosphorylation in vivo is dependent on the degree of reduction of the intramitochondrial reducing power ([NADH]/[NAD+], cytoplasmic energy state ([ATP]/[ADP][Pi]) and intracellular oxygen pressure. Each parameter is independently regulated, and increased reducing power by activating the mitochondrial dehydrogenases allows higher energy state at a given rate of ATP synthesis or a higher rate of ATP synthesis at a given energy state. The mitochondrial respiratory rate is determined by demand, i.e., the rate of ATP utilization by the cell, while the cellular energy state at that demand level is determined by supply, i.e., activity of the dehydrogenases expressed as [NADH]/[NAD+] and of cytoplasmic oxygen pressure.

Adenosine Diphosphate↗
PubMed1984

Effects of excessive noradrenaline on cardiac mitochondrial calcium transport and oxidative phosphorylation.

Mitochondrial oxidative phosphorylation, calcium transport activity and calcium content were investigated in dog hearts injured by excessive noradrenaline (NA). Diffuse cardiac injury was produced by a 5-hour infusion of NA (2 or 5 micrograms/kg/min), and the injury was evaluated based on ECG and hemodynamic changes. Mitochondrial calcium uptake and binding activities measured in the presence of ATP showed no significant differences between the control and NA groups. However, the calcium content of heart mitochondria isolated from the NA groups, state 3 respiration and the respiratory control index were significantly depressed without any change in the ADP/O ratio. These results suggest that excessive NA causes the intracellular calcium overload and the depression of mitochondrial respiration, and the both of these changes may play a key role in the pathogenesis of myocardial injury through the insufficient control of cytosolic calcium levels.

Animals↗
PubMed2001

An introduction: oxidative phosphorylation diseases.

Oxidative phosphorylation (OXPHOS) is responsible for producing much of the adenosine triphosphate that is required by cells. The OXPHOS pathway incorporates over 100 polypeptides whose genes are located in either the nuclear DNA or the mitochondrial DNA (mtDNA). The expression of these genes and the assembly of the five OXPHOS enzyme complexes (complexes I to V) is a highly ordered and coordinated process. A broad array of human diseases result from mutations in either the nuclear or mtDNA genes or even in the systems that coordinate their interactions. Consequently, OXPHOS diseases can have complex inheritance patterns and a wide spectrum of clinical presentations.

Education, Medical, Continuing↗
PubMed2000

Secondary carnitine deficiency and impaired docosahexaenoic (22:6n-3) acid synthesis: a common denominator in the pathophysiology of diseases of oxidative phosphorylation and beta-oxidation.

A critical analysis of the literature of mitochondrial disorders reveals that genetic diseases of oxidative phosphorylation are often associated with impaired beta-oxidation, and vice versa, and preferentially affect brain, retina, heart and skeletal muscle, tissues which depend on docosahexaenoic (22:6n-3)-containing phospholipids for functionality. Evidence suggests that an increased NADH/NAD(+) ratio generated by reduced flux through the respiratory chain inhibits beta-oxidation, producing secondary carnitine deficiency while increasing reactive oxygen species and depleting alpha-tocopherol (alpha-TOC). These events result in impairment of the recently elucidated mitochondrial pathway for synthesis of 22:6n-3-containing phospholipids, since carnitine and alpha-TOC are involved in their biosynthesis. Therapeutic supplementation with 22:6n-3 and alpha-TOC is suggested.

Animals↗
PubMed1991

Distribution of control of oxidative phosphorylation in mitochondria oxidizing NAD-linked substrates.

The flux control distribution of the net rate of state 3 respiration was determined in heart and kidney mitochondria incubated with low concentrations of pyruvate (0.5 mM) or 2-oxoglutarate (1 mM), and in conditions that led to activation of NAD-linked dehydrogenases, i.e., high substrate or Ca2+ concentrations. Control of flux was exerted by the ATP/ADP carrier (flux control coefficient, ci = 0.37) and Site 1 of the respiratory chain (ci = 0.28) when dehydrogenase activity was low. Control of the process shifted to the ATP synthase (ci = 0.32) and the Pi carrier (Ci = 0.27) when dehydrogenases were activated by high pyruvate and high Ca2+. The changes in the control exerted by the ATP/ADP carrier and the ATP synthase were not due to changes in the transmembrane potential, nor to a modification of intramitochondrial ATP/ADP ratios. Applying the summation theorem of the control analysis, it was found that at low Ca2+ and pyruvate concentrations the dehydrogenases shared the control of state 3 respiration with other steps. The NAD-linked dehydrogenases did not exert any significant control at high Ca2+ or high pyruvate concentrations.

Animals↗