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Panja S, Nahomi RB, Rankenberg J, Michel CR, Nagaraj RH. Thiol-Mediated Enhancement of N ε-Acetyllysine Formation in Lens Proteins. ACS Chem Biol 2024; 19:1495-1505. [PMID: 38904252 DOI: 10.1021/acschembio.4c00174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
Lysine acetylation (AcK) is a prominent post-translational modification in eye lens crystallins. We have observed that AcK formation is preferred in some lysine residues over others in crystallins. In this study, we have investigated the role of thiols in such AcK formation. Upon incubation with acetyl-CoA (AcCoA), αA-Crystallin, which contains two cysteine residues, showed significantly higher levels of AcK than αB-Crystallin, which lacks cysteine residues. Incubation with thiol-rich γS-Crystallin resulted in higher AcK formation in αB-Crystallin from AcCoA. External free thiol (glutathione and N-acetyl cysteine) increased the AcK content in AcCoA-incubated αB-Crystallin. Reductive alkylation of cysteine residues significantly decreased (p < 0.001) the AcCoA-mediated AcK formation in αA-Crystallin. Introduction of cysteine residues within ∼5 Å of lysine residues (K92C, E99C, and V169C) in αB-Crystallin followed by incubation with AcCoA resulted in a 3.5-, 1.3- and 1.3-fold increase in the AcK levels when compared to wild-type αB-Crystallin, respectively. Together, these results suggested that AcK formation in α-Crystallin is promoted by the proximal cysteine residues and protein-free thiols through an S → N acetyl transfer mechanism.
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2
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Kloska SM, Pałczyński K, Marciniak T, Talaśka T, Wysocki BJ, Davis P, Wysocki TA. Integrating glycolysis, citric acid cycle, pentose phosphate pathway, and fatty acid beta-oxidation into a single computational model. Sci Rep 2023; 13:14484. [PMID: 37660197 PMCID: PMC10475038 DOI: 10.1038/s41598-023-41765-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 08/31/2023] [Indexed: 09/04/2023] Open
Abstract
The metabolic network of a living cell is highly intricate and involves complex interactions between various pathways. In this study, we propose a computational model that integrates glycolysis, the pentose phosphate pathway (PPP), the fatty acids beta-oxidation, and the tricarboxylic acid cycle (TCA cycle) using queueing theory. The model utilizes literature data on metabolite concentrations and enzyme kinetic constants to calculate the probabilities of individual reactions occurring on a microscopic scale, which can be viewed as the reaction rates on a macroscopic scale. However, it should be noted that the model has some limitations, including not accounting for all the reactions in which the metabolites are involved. Therefore, a genetic algorithm (GA) was used to estimate the impact of these external processes. Despite these limitations, our model achieved high accuracy and stability, providing real-time observation of changes in metabolite concentrations. This type of model can help in better understanding the mechanisms of biochemical reactions in cells, which can ultimately contribute to the prevention and treatment of aging, cancer, metabolic diseases, and neurodegenerative disorders.
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Affiliation(s)
- Sylwester M Kloska
- Faculty of Medicine, Nicolaus Copernicus University Ludwik Rydygier Collegium Medicum, 85-094, Bydgoszcz, Poland.
| | - Krzysztof Pałczyński
- Faculty of Telecommunications, Computer Science and Electrical Engineering, Bydgoszcz University of Science and Technology, 85-796, Bydgoszcz, Poland
| | - Tomasz Marciniak
- Faculty of Telecommunications, Computer Science and Electrical Engineering, Bydgoszcz University of Science and Technology, 85-796, Bydgoszcz, Poland
| | - Tomasz Talaśka
- Faculty of Telecommunications, Computer Science and Electrical Engineering, Bydgoszcz University of Science and Technology, 85-796, Bydgoszcz, Poland
| | - Beata J Wysocki
- Department of Biology, University of Nebraska at Omaha, Omaha, NE, 68182, USA
| | - Paul Davis
- Department of Biology, University of Nebraska at Omaha, Omaha, NE, 68182, USA
| | - Tadeusz A Wysocki
- Faculty of Telecommunications, Computer Science and Electrical Engineering, Bydgoszcz University of Science and Technology, 85-796, Bydgoszcz, Poland
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Omaha, NE, 68182, USA
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3
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Wilson DF, Matschinsky FM. Integration of Eukaryotic Energy Metabolism: The Intramitochondrial and Cytosolic Energy States ([ATP] f/[ADP] f[Pi]). Int J Mol Sci 2022; 23:ijms23105550. [PMID: 35628359 PMCID: PMC9146745 DOI: 10.3390/ijms23105550] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 05/06/2022] [Accepted: 05/07/2022] [Indexed: 11/16/2022] Open
Abstract
Maintaining a robust, stable source of energy for doing chemical and physical work is essential to all living organisms. In eukaryotes, metabolic energy (ATP) production and consumption occurs in two separate compartments, the mitochondrial matrix and the cytosol. As a result, understanding eukaryotic metabolism requires knowledge of energy metabolism in each compartment and how metabolism in the two compartments is coordinated. Central to energy metabolism is the adenylate energy state ([ATP]/[ADP][Pi]). ATP is synthesized by oxidative phosphorylation (mitochondrial matrix) and glycolysis (cytosol) and each compartment provides the energy to do physical work and to drive energetically unfavorable chemical syntheses. The energy state in the cytoplasmic compartment has been established by analysis of near equilibrium metabolic reactions localized in that compartment. In the present paper, analysis is presented for energy-dependent reactions localized in the mitochondrial matrix using data obtained from both isolated mitochondria and intact tissues. It is concluded that the energy state ([ATP]f/[ADP]f[Pi]) in the mitochondrial matrix, calculated from the free (unbound) concentrations, is not different from the energy state in the cytoplasm. Corollaries are: (1) ADP in both the cytosol and matrix is selectively bound and the free concentrations are much lower than the total measured concentrations; and (2) under physiological conditions, the adenylate energy states in the mitochondrial matrix and cytoplasm are not substantially different.
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4
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The yeast mitochondrial succinylome: Implications for regulation of mitochondrial nucleoids. J Biol Chem 2021; 297:101155. [PMID: 34480900 PMCID: PMC8477199 DOI: 10.1016/j.jbc.2021.101155] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 08/23/2021] [Accepted: 08/30/2021] [Indexed: 11/22/2022] Open
Abstract
Acylation modifications, such as the succinylation of lysine, are post-translational modifications and a powerful means of regulating protein activity. Some acylations occur nonenzymatically, driven by an increase in the concentration of acyl group donors. Lysine succinylation has a profound effect on the corresponding site within the protein, as it dramatically changes the charge of the residue. In eukaryotes, it predominantly affects mitochondrial proteins because the donor of succinate, succinyl-CoA, is primarily generated in the tricarboxylic acid cycle. Although numerous succinylated mitochondrial proteins have been identified in Saccharomyces cerevisiae, a more detailed characterization of the yeast mitochondrial succinylome is still lacking. Here, we performed a proteomic MS analysis of purified yeast mitochondria and detected 314 succinylated mitochondrial proteins with 1763 novel succinylation sites. The mitochondrial nucleoid, a complex of mitochondrial DNA and mitochondrial proteins, is one of the structures whose protein components are affected by succinylation. We found that Abf2p, the principal component of mitochondrial nucleoids responsible for compacting mitochondrial DNA in S. cerevisiae, can be succinylated in vivo on at least thirteen lysine residues. Abf2p succinylation in vitro inhibits its DNA-binding activity and reduces its sensitivity to digestion by the ATP-dependent ScLon protease. We conclude that changes in the metabolic state of a cell resulting in an increase in the concentration of tricarboxylic acid intermediates may affect mitochondrial functions.
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Bonds AC, Yuan T, Werman JM, Jang J, Lu R, Nesbitt NM, Garcia-Diaz M, Sampson NS. Post-translational Succinylation of Mycobacterium tuberculosis Enoyl-CoA Hydratase EchA19 Slows Catalytic Hydration of Cholesterol Catabolite 3-Oxo-chol-4,22-diene-24-oyl-CoA. ACS Infect Dis 2020; 6:2214-2224. [PMID: 32649175 DOI: 10.1021/acsinfecdis.0c00329] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cholesterol is a major carbon source for Mycobacterium tuberculosis (Mtb) during infection, and cholesterol utilization plays a significant role in persistence and virulence within host macrophages. Elucidating the mechanism by which cholesterol is degraded may permit the identification of new therapeutic targets. Here, we characterized EchA19 (Rv3516), an enoyl-CoA hydratase involved in cholesterol side-chain catabolism. Steady-state kinetics assays demonstrated that EchA19 preferentially hydrates cholesterol enoyl-CoA metabolite 3-oxo-chol-4,22-diene-24-oyl-CoA, an intermediate of side-chain β-oxidation. In addition, succinyl-CoA, a downstream catabolite of propionyl-CoA that forms during cholesterol degradation, covalently modifies targeted mycobacterial proteins, including EchA19. Inspection of a 1.9 Å resolution X-ray crystallography structure of Mtb EchA19 suggests that succinylation of Lys132 and Lys139 may perturb enzymatic activity by modifying the entrance to the substrate binding site. Treatment of EchA19 with succinyl-CoA revealed that these two residues are hotspots for succinylation. Replacement of these specific lysine residues with negatively charged glutamate reduced the rate of catalytic hydration of 3-oxo-chol-4,22-diene-24-oyl-CoA by EchA19, as does succinylation of EchA19. Our findings suggest that succinylation is a negative feedback regulator of cholesterol metabolism, thereby adding another layer of complexity to Mtb physiology in the host. These regulatory pathways are potential noncatabolic targets for antimicrobial drugs.
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Affiliation(s)
- Amber C. Bonds
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794-8651
| | - Tianao Yuan
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400
| | - Joshua M. Werman
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400
| | - Jungwon Jang
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400
| | - Rui Lu
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400
| | - Natasha M. Nesbitt
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400
| | - Miguel Garcia-Diaz
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794-8651
| | - Nicole S. Sampson
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400
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6
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Aleshin VA, Mkrtchyan GV, Kaehne T, Graf AV, Maslova MV, Bunik VI. Diurnal regulation of the function of the rat brain glutamate dehydrogenase by acetylation and its dependence on thiamine administration. J Neurochem 2020; 153:80-102. [PMID: 31886885 DOI: 10.1111/jnc.14951] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 12/19/2019] [Accepted: 12/23/2019] [Indexed: 12/20/2022]
Abstract
Glutamate dehydrogenase (GDH) is essential for the brain function and highly regulated, according to its role in metabolism of the major excitatory neurotransmitter glutamate. Here we show a diurnal pattern of the GDH acetylation in rat brain, associated with specific regulation of GDH function. Mornings the acetylation levels of K84 (near the ADP site), K187 (near the active site), and K503 (GTP-binding) are highly correlated. Evenings the acetylation levels of K187 and K503 decrease, and the correlations disappear. These daily variations in the acetylation adjust the GDH responses to the enzyme regulators. The adjustment is changed when the acetylation of K187 and K503 shows no diurnal variations, as in the rats after a high dose of thiamine. The regulation of GDH function by acetylation is confirmed in a model system, where incubation of the rat brain GDH with acetyl-CoA changes the enzyme responses to GTP and ADP, decreasing the activity at subsaturating concentrations of substrates. Thus, the GDH acetylation may support cerebral homeostasis, stabilizing the enzyme function during diurnal oscillations of the brain metabolome. Daytime and thiamine interact upon the (de)acetylation of GDH in vitro. Evenings the acetylation of GDH from control animals increases both IC50 GTP and EC50 ADP . Mornings the acetylation of GDH from thiamine-treated animals increases the enzyme IC50 GTP . Molecular mechanisms of the GDH regulation by acetylation of specific residues are proposed. For the first time, diurnal and thiamine-dependent changes in the allosteric regulation of the brain GDH due to the enzyme acetylation are shown.
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Affiliation(s)
- Vasily A Aleshin
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia.,A.N.Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Garik V Mkrtchyan
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia
| | - Thilo Kaehne
- Institute of Experimental Internal Medicine, Otto-von-Guericke University, Magdeburg, Germany
| | - Anastasia V Graf
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.,Faculty of Nano-, Bio-, Informational, Cognitive and Socio-humanistic Sciences and Technologies at Moscow Institute of Physics and Technology, Moscow, Russia
| | - Maria V Maslova
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Victoria I Bunik
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia.,A.N.Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
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7
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Leung MCK, Meyer JN. Mitochondria as a target of organophosphate and carbamate pesticides: Revisiting common mechanisms of action with new approach methodologies. Reprod Toxicol 2019; 89:83-92. [PMID: 31315019 PMCID: PMC6766410 DOI: 10.1016/j.reprotox.2019.07.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 06/19/2019] [Accepted: 07/09/2019] [Indexed: 01/01/2023]
Abstract
Mitochondrial toxicity has been proposed as a potential cause of developmental defects in humans. We evaluated 51 organophosphate and carbamate pesticides using the U.S. EPA ToxCast and Tox21 databases. Only a small number of them bind directly to cholinesterases in the parent form. The hydrophobicity of organophosphate pesticides is correlated significantly to TSPO binding affinity, mitochondrial membrane potential reduction in HepG2 cells, and developmental toxicity in Caenorhabditis elegans and Danio rerio (p < 0.05). Structural analysis suggests that in some cases the Krebs cycle is a potential target of organophosphate and carbamate exposure at early life stages. The results support the hypothesis that mitochondrial effects of some organophosphate pesticides-particularly those that require enzymatic activation to the oxon form-may augment the documented effects of disruption of acetylcholine signaling. This study provides a proof of concept for applying new approach methodologies to interrogate mechanisms of action for cumulative risk assessment.
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Affiliation(s)
- Maxwell C K Leung
- Department of Environmental Toxicology, University of California, Davis, CA, United States; Nicholas School of the Environment, Duke University, Durham, NC, United States.
| | - Joel N Meyer
- Nicholas School of the Environment, Duke University, Durham, NC, United States
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Dikalov SI, Dikalova AE. Crosstalk Between Mitochondrial Hyperacetylation and Oxidative Stress in Vascular Dysfunction and Hypertension. Antioxid Redox Signal 2019; 31:710-721. [PMID: 30618267 PMCID: PMC6708267 DOI: 10.1089/ars.2018.7632] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Significance: Vascular dysfunction plays a key role in the development of arteriosclerosis, heart disease, and hypertension, which causes one-third of deaths worldwide. Vascular oxidative stress and metabolic disorders contribute to vascular dysfunction, leading to impaired vasorelaxation, vascular hypertrophy, fibrosis, and aortic stiffening. Mitochondria are critical in the regulation of metabolic and antioxidant functions; therefore, mitochondria-targeted treatments could be beneficial. Recent Advances: Vascular dysfunction is crucial in hypertension pathophysiology and exhibits bidirectional relationship. Metabolic disorders and oxidative stress contribute to the pathogenesis of vascular dysfunction and hypertension, which are associated with mitochondrial impairment and hyperacetylation. Mitochondrial deacetylase Sirtuin 3 (Sirt3) is critical in the regulation of metabolic and antioxidant functions. Clinical studies show that cardiovascular disease risk factors reduce Sirt3 level and Sirt3 declines with age, paralleling the increased incidence of cardiovascular disease and hypertension. An imbalance between mitochondrial acetylation and reduced Sirt3 activity contributes to mitochondrial dysfunction and oxidative stress. We propose that mitochondrial hyperacetylation drives a vicious cycle between metabolic disorders and mitochondrial oxidative stress, promoting vascular dysfunction and hypertension. Critical Issues: The mechanisms of mitochondrial dysfunction are still obscure in human hypertension. Mitochondrial hyperacetylation and oxidative stress contribute to mitochondrial dysfunction; however, regulation of mitochondrial acetylation, the role of GCN5L1 (acetyl-CoA-binding protein promoting acetyltransferase protein acetylation) acetyltransferase, Sirt3 deacetylase, and acetylation of specific proteins require further investigations. Future Directions: There is an urgent need to define molecular mechanisms and the pathophysiological role of mitochondrial hyperacetylation, identify novel pharmacological targets, and develop therapeutic approaches to reduce this phenomenon.
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Affiliation(s)
- Sergey I Dikalov
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Anna E Dikalova
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
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9
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Ringel AE, Tucker SA, Haigis MC. Chemical and Physiological Features of Mitochondrial Acylation. Mol Cell 2019; 72:610-624. [PMID: 30444998 DOI: 10.1016/j.molcel.2018.10.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 09/15/2018] [Accepted: 10/15/2018] [Indexed: 01/09/2023]
Abstract
Growing appreciation of the diversity of post-translational modifications (PTMs) in the mitochondria necessitates reevaluation of the roles these modifications play in both health and disease. Compared to the cytosol and nucleus, the mitochondrial proteome is highly acylated, and remodeling of the mitochondrial "acylome" is a key adaptive mechanism that regulates fundamental aspects of mitochondrial biology. It is clear that we need to understand the underlying chemistry that regulates mitochondrial acylation, as well as how chemical properties of the acyl chain impact biological functions. Here, we dissect the sources of PTMs in the mitochondria, review major mitochondrial pathways that control levels of PTMs, and highlight how sirtuin enzymes respond to the bioenergetic state of the cell via NAD+ availability to regulate mitochondrial biology. By providing a framework connecting the chemistry of these modifications, their biochemical consequences, and the pathways that regulate the levels of acyl PTMs, we will gain a deeper understanding of the physiological significance of mitochondrial acylation and its role in mitochondrial adaptation.
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Affiliation(s)
- Alison E Ringel
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Ludwig Center for Cancer Research at Harvard, Boston, MA 02115, USA
| | - Sarah A Tucker
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Ludwig Center for Cancer Research at Harvard, Boston, MA 02115, USA
| | - Marcia C Haigis
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Ludwig Center for Cancer Research at Harvard, Boston, MA 02115, USA.
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10
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Moreno-Sánchez R, Marín-Hernández Á, Gallardo-Pérez JC, Vázquez C, Rodríguez-Enríquez S, Saavedra E. Control of the NADPH supply and GSH recycling for oxidative stress management in hepatoma and liver mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:1138-1150. [PMID: 30053395 DOI: 10.1016/j.bbabio.2018.07.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/19/2018] [Accepted: 07/22/2018] [Indexed: 01/30/2023]
Abstract
To unveil what controls mitochondrial ROS detoxification, the NADPH supply and GSH/GSSG recycling for oxidative stress management were analyzed in cancer and non-cancer mitochondria. Therefore, proteomic and kinetomic analyses were carried out of the mitochondrial (i) NADPH producing and (ii) GSH/GSSG recycling enzymes associated to oxidative stress management. The protein contents of the eight enzymes analyzed were similar or even higher in AS-30D rat hepatoma mitochondria (HepM) than in rat liver (RLM) and rat heart (RHM) mitochondria, suggesting that the NADPH/GSH/ROS pathway was fully functional in cancer mitochondria. The Vmax values of IDH-2 were much greater than those of GDH, TH and ME, suggesting that IDH-2 is the predominant NADPH producer in the three mitochondrial types; in fact, the GDH reverse reaction was favored. The Vmax values of GR and GPx were lower in HepM than in RLM, suggesting that the oxidative stress management is compromised in cancer mitochondria. The Km values of IDH-2, GR and GPx were all similar among the different mitochondrial types. Kinetic modeling revealed that the oxidative stress management was mainly controlled by GR, GPx and IDH. Modeling and experimentation also revealed that, due to their higher IDH-2 activity and lower GPx activity presumably by acetylation, HepM (i) showed higher steady-state NADPH levels; (ii) required greater peroxide concentrations to achieve reliable steady-state fluxes and metabolite concentration; and (iii) endured higher peroxide concentrations without collapsing their GSH/GSSG ratios. Then, to specifically prompt lower GSH/GSSG ratios under oxidative stress thus compromising cancer mitochondria functioning, GPx should be re-activated.
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Affiliation(s)
- Rafael Moreno-Sánchez
- Instituto Nacional de Cardiología, Departamento de Bioquímica, Ciudad de México 14080, Tlalpan, Mexico.
| | - Álvaro Marín-Hernández
- Instituto Nacional de Cardiología, Departamento de Bioquímica, Ciudad de México 14080, Tlalpan, Mexico
| | | | - Citlali Vázquez
- Instituto Nacional de Cardiología, Departamento de Bioquímica, Ciudad de México 14080, Tlalpan, Mexico
| | - Sara Rodríguez-Enríquez
- Instituto Nacional de Cardiología, Departamento de Bioquímica, Ciudad de México 14080, Tlalpan, Mexico
| | - Emma Saavedra
- Instituto Nacional de Cardiología, Departamento de Bioquímica, Ciudad de México 14080, Tlalpan, Mexico
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11
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Davies MN, Kjalarsdottir L, Thompson JW, Dubois LG, Stevens RD, Ilkayeva OR, Brosnan MJ, Rolph TP, Grimsrud PA, Muoio DM. The Acetyl Group Buffering Action of Carnitine Acetyltransferase Offsets Macronutrient-Induced Lysine Acetylation of Mitochondrial Proteins. Cell Rep 2015; 14:243-54. [PMID: 26748706 DOI: 10.1016/j.celrep.2015.12.030] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 10/26/2015] [Accepted: 12/03/2015] [Indexed: 11/25/2022] Open
Abstract
Lysine acetylation (AcK), a posttranslational modification wherein a two-carbon acetyl group binds covalently to a lysine residue, occurs prominently on mitochondrial proteins and has been linked to metabolic dysfunction. An emergent theory suggests mitochondrial AcK occurs via mass action rather than targeted catalysis. To test this hypothesis, we performed mass spectrometry-based acetylproteomic analyses of quadriceps muscles from mice with skeletal muscle-specific deficiency of carnitine acetyltransferase (CrAT), an enzyme that buffers the mitochondrial acetyl-CoA pool by converting short-chain acyl-CoAs to their membrane permeant acylcarnitine counterparts. CrAT deficiency increased tissue acetyl-CoA levels and susceptibility to diet-induced AcK of broad-ranging mitochondrial proteins, coincident with diminished whole body glucose control. Sub-compartment acetylproteome analyses of muscles from obese mice and humans showed remarkable overrepresentation of mitochondrial matrix proteins. These findings reveal roles for CrAT and L-carnitine in modulating the muscle acetylproteome and provide strong experimental evidence favoring the nonenzymatic carbon pressure model of mitochondrial AcK.
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Affiliation(s)
- Michael N Davies
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
| | - Lilja Kjalarsdottir
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
| | - J Will Thompson
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27701, USA; Proteomics and Metabolomics Shared Resource, Duke University, Durham, NC 27701, USA
| | - Laura G Dubois
- Proteomics and Metabolomics Shared Resource, Duke University, Durham, NC 27701, USA
| | - Robert D Stevens
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
| | - Olga R Ilkayeva
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
| | - M Julia Brosnan
- CV and Metabolic Diseases (CVMED), a Pfizer Research Unit, Cambridge, MA 02139, USA
| | - Timothy P Rolph
- CV and Metabolic Diseases (CVMED), a Pfizer Research Unit, Cambridge, MA 02139, USA
| | - Paul A Grimsrud
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
| | - Deborah M Muoio
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA; Department of Medicine, Duke University, Durham, NC 27701, USA; Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27701, USA.
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12
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Simic Z, Weiwad M, Schierhorn A, Steegborn C, Schutkowski M. The ɛ-Amino Group of Protein Lysine Residues Is Highly Susceptible to Nonenzymatic Acylation by Several Physiological Acyl-CoA Thioesters. Chembiochem 2015; 16:2337-47. [PMID: 26382620 DOI: 10.1002/cbic.201500364] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Indexed: 01/04/2023]
Abstract
Mitochondrial enzymes implicated in the pathophysiology of diabetes, cancer, and metabolic syndrome are highly regulated by acetylation. However, mitochondrial acetyltransferases have not been identified. Here, we show that acetylation and also other acylations are spontaneous processes that depend on pH value, acyl-CoA concentration and the chemical nature of the acyl residue. In the case of a peptide derived from carbamoyl phosphate synthetase 1, the rates of succinylation and glutarylation were up to 150 times than for acetylation. These results were confirmed by using the protein substrate cyclophilin A (CypA). Deacylation experiments revealed that SIRT3 exhibits deacetylase activity but is not able to remove any of the succinyl groups from CypA, whereas SIRT5 is an effective protein desuccinylase. Thus, the acylation landscape on lysine residues might largely depend on the enzymatic activity of specific sirtuins, and the availability and reactivity of acyl-CoA compounds.
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Affiliation(s)
- Zeljko Simic
- Department of Enzymology, Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 3, 06120, Halle, Germany
| | - Matthias Weiwad
- Department of Enzymology, Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 3, 06120, Halle, Germany
| | - Angelika Schierhorn
- Department of Enzymology, Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 3, 06120, Halle, Germany
| | - Clemens Steegborn
- Department of Biochemistry, University of Bayreuth, Universitätsstraße 30, 95440, Bayreuth, Germany
| | - Mike Schutkowski
- Department of Enzymology, Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 3, 06120, Halle, Germany.
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13
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Abstract
Cellular proteins are decorated with a wide range of acetyl and other acyl modifications. Many studies have demonstrated regulation of site-specific acetylation by acetyltransferases and deacetylases. Acylation is emerging as a new type of lysine modification, but less is known about its overall regulatory role. Furthermore, the mechanisms of lysine acylation, its overlap with protein acetylation, and how it influences cellular function are major unanswered questions in the field. In this review, we discuss the known roles of acetyltransferases and deacetylases and the sirtuins as a conserved family of a nicotinamide adenine dinucleotide (NAD⁺)-dependent protein deacylases that are important for response to cellular stress and homeostasis. We also consider the evidence for an emerging idea of nonenzymatic protein acylation. Finally, we put forward the hypothesis that protein acylation is a form of protein "carbon stress" that the deacylases evolved to remove as a part of a global protein quality-control network.
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14
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Berndt N, Holzhütter HG, Bulik S. Implications of enzyme deficiencies on mitochondrial energy metabolism and reactive oxygen species formation of neurons involved in rotenone-induced Parkinson's disease: a model-based analysis. FEBS J 2013; 280:5080-93. [PMID: 23937586 DOI: 10.1111/febs.12480] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 07/19/2013] [Accepted: 08/07/2013] [Indexed: 12/21/2022]
Abstract
Steadily growing experimental evidence suggests that mitochondrial dysfunction plays a key role in the age-dependent impairment of nerve cells underlying several neurodegenerative diseases. In particular, the citric acid cycle enzyme complex α-ketoglutarate dehydrogenase (KGDHC) and respiratory chain complex I of the respiratory chain often show reduced activities in the dopaminergic neurons involved in Parkinson's disease, both giving rise to an impaired mitochondrial energy metabolism as demonstrated in a number of in vitro studies with cell lines as well as isolated mitochondria. To understand the metabolic regulation underlying these experimental findings we used a detailed kinetic model of mitochondrial energy metabolism. First, we investigated the effect of complex I inhibition on energy production and formation of reactive oxygen species (ROS). Next, we applied the model to a situation where both KGDHC and complex I exhibit reduced activities. These calculations reveal synergistic effects with respect to the energy metabolism but antagonistic effects with respect to ROS formation: the drop in the ATP production capacity is more pronounced than at inhibition of either enzyme complex alone. Interestingly, however, the reduction state of the ROS-generating sites of the impaired complex I becomes significantly lowered if additionally the activity of the KGDHC is reduced. We discuss the pathophysiological consequences of these intriguing findings.
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Affiliation(s)
- Nikolaus Berndt
- Institute of Biochemistry, University Medicine Berlin - Charité, Germany
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15
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Wagner GR, Payne RM. Widespread and enzyme-independent Nε-acetylation and Nε-succinylation of proteins in the chemical conditions of the mitochondrial matrix. J Biol Chem 2013; 288:29036-45. [PMID: 23946487 DOI: 10.1074/jbc.m113.486753] [Citation(s) in RCA: 391] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Alterations in mitochondrial protein acetylation are implicated in the pathophysiology of diabetes, the metabolic syndrome, mitochondrial disorders, and cancer. However, a viable mechanism responsible for the widespread acetylation in mitochondria remains unknown. Here, we demonstrate that the physiologic pH and acyl-CoA concentrations of the mitochondrial matrix are sufficient to cause dose- and time-dependent, but enzyme-independent acetylation and succinylation of mitochondrial and nonmitochondrial proteins in vitro. These data suggest that protein acylation in mitochondria may be a chemical event facilitated by the alkaline pH and high concentrations of reactive acyl-CoAs present in the mitochondrial matrix. Although these results do not exclude the possibility of enzyme-mediated protein acylation in mitochondria, they demonstrate that such a mechanism may not be required in its unique chemical environment. These findings may have implications for the evolutionary roles that the mitochondria-localized SIRT3 deacetylase and SIRT5 desuccinylase have in the maintenance of metabolic health.
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Affiliation(s)
- Gregory R Wagner
- From the Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202 and
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16
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Klemcke HG, DeKroon RM, Mocanu M, Robinette JB, Alzate O. Cardiac mitochondrial proteomic expression in inbred rat strains divergent in survival time after hemorrhage. Physiol Genomics 2013; 45:243-55. [PMID: 23386204 DOI: 10.1152/physiolgenomics.00118.2012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We have previously identified inbred rat strains differing in survival time to a severe controlled hemorrhage (StaH). In efforts to identify cellular mechanisms and ultimately genes that are important contributors to enhanced STaH, we conducted a study to characterize potential differences in cardiac mitochondrial proteins in these rats. Inbred rats from three strains [Brown Norway/Medical College of Wisconsin (BN); Dark Agouti (DA), and Fawn Hooded Hypertensive (FHH)] with different StaH (DA = FHH > BN) were assigned to one of three treatment groups (n = 4/strain): nonoperated controls, surgically catheterized rats, or rats surgically catheterized and hemorrhaged 24 h postsurgery. Rats were euthanized 30 min after handling or 30 min after initiation of a 26 min hemorrhage. After euthanasia, hearts were removed and mitochondria isolated. Differential protein expression was determined using 2D DIGE-based Quantitative Intact Proteomics and proteins identified by MALDI/TOF mass spectrometry. Hundreds of proteins (791) differed among inbred rat strains (P ≤ 0.038), and of these 81 were identified. Thirty-eight were unique proteins and 43 were apparent isoforms. For DA rats (longest STaH), 36 proteins increased and 30 decreased compared with BN (shortest STaH). These 81 proteins were associated with lipid (e.g., acyl CoA dehydrogenase) and carbohydrate (e.g., fumarase) metabolism, oxidative phosphorylation (e.g., ubiquinol-cytochrome C reductase), ATP synthesis (F1 ATPase), and H2S synthesis (3-mercaptopyruvate sulfurtransferase). Although we cannot make associations between these identified mitochondrial proteins and StaH, our data do provide evidence for future candidate proteins with which to consider such associations.
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Affiliation(s)
- Harold G Klemcke
- U.S. Army Institute of Surgical Research, Fort Sam Houston, Texas 78234, USA.
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17
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Kinetic Modeling of the Mitochondrial Energy Metabolism of Neuronal Cells: The Impact of Reduced α-Ketoglutarate Dehydrogenase Activities on ATP Production and Generation of Reactive Oxygen Species. Int J Cell Biol 2012; 2012:757594. [PMID: 22719765 PMCID: PMC3376505 DOI: 10.1155/2012/757594] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 04/11/2012] [Indexed: 11/17/2022] Open
Abstract
Reduced activity of brain α-ketoglutarate dehydrogenase complex (KGDHC) occurs in a number of neurodegenerative diseases like Parkinson's disease and Alzheimer's disease. In order to quantify the relation between diminished KGDHC activity and the mitochondrial ATP generation, redox state, transmembrane potential, and generation of reactive oxygen species (ROS) by the respiratory chain (RC), we developed a detailed kinetic model. Model simulations revealed a threshold-like decline of the ATP production rate at about 60% inhibition of KGDHC accompanied by a significant increase of the mitochondrial membrane potential. By contrast, progressive inhibition of the enzyme aconitase had only little impact on these mitochondrial parameters. As KGDHC is susceptible to ROS-dependent inactivation, we also investigated the reduction state of those sites of the RC proposed to be involved in ROS production. The reduction state of all sites except one decreased with increasing degree of KGDHC inhibition suggesting an ROS-reducing effect of KGDHC inhibition. Our model underpins the important role of reduced KGDHC activity in the energetic breakdown of neuronal cells during development of neurodegenerative diseases.
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18
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Denton RM. Regulation of mitochondrial dehydrogenases by calcium ions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1309-16. [PMID: 19413950 DOI: 10.1016/j.bbabio.2009.01.005] [Citation(s) in RCA: 607] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 11/21/2008] [Revised: 01/08/2009] [Accepted: 01/09/2009] [Indexed: 11/24/2022]
Abstract
Studies in Bristol in the 1960s and 1970s, led to the recognition that four mitochondrial dehydrogenases are activated by calcium ions. These are FAD-glycerol phosphate dehydrogenase, pyruvate dehydrogenase, NAD-isocitrate dehydrogenase and oxoglutarate dehydrogenase. FAD-glycerol phosphate dehydrogenase is located on the outer surface of the inner mitochondrial membrane and is influenced by changes in cytoplasmic calcium ion concentration. The other three enzymes are located within mitochondria and are regulated by changes in mitochondrial matrix calcium ion concentration. These and subsequent studies on purified enzymes, mitochondria and intact cell preparations have led to the widely accepted view that the activation of these enzymes is important in the stimulation of the respiratory chain and hence ATP supply under conditions of increased ATP demand in many stimulated mammalian cells. The effects of calcium ions on FAD-isocitrate dehydrogenase involve binding to an EF-hand binding motif within this enzyme but the binding sites involved in the effects of calcium ions on the three intramitochondrial dehydrogenases remain to be fully established. It is also emphasised in this article that these three dehydrogenases appear only to be regulated by calcium ions in vertebrates and that this raises some interesting and potentially important developmental issues.
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Affiliation(s)
- Richard M Denton
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 ITD, UK.
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19
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Mogilevskaya E, Demin O, Goryanin I. Kinetic model of mitochondrial Krebs cycle: unraveling the mechanism of salicylate hepatotoxic effects. J Biol Phys 2006; 32:245-71. [PMID: 19669466 PMCID: PMC2651525 DOI: 10.1007/s10867-006-9015-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Accepted: 06/02/2006] [Indexed: 10/24/2022] Open
Abstract
This paper studies the effect of salicylate on the energy metabolism of mitochondria using in silico simulations. A kinetic model of the mitochondrial Krebs cycle is constructed using information on the individual enzymes. Model parameters for the rate equations are estimated using in vitro experimental data from the literature. Enzyme concentrations are determined from data on respiration in mitochondrial suspensions containing glutamate and malate. It is shown that inhibition in succinate dehydrogenase and alpha-ketoglutarate dehydrogenase by salicylate contributes substantially to the cumulative inhibition of the Krebs cycle by salicylates. Uncoupling of oxidative phosphorylation has little effect and coenzyme A consumption in salicylates transformation processes has an insignificant effect on the rate of substrate oxidation in the Krebs cycle. It is found that the salicylate-inhibited Krebs cycle flux can be increased by flux redirection through addition of external glutamate and malate, and depletion in external alpha-ketoglutarate and glycine concentrations.
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Affiliation(s)
- Ekaterina Mogilevskaya
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 Russia
| | - Oleg Demin
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 Russia
| | - Igor Goryanin
- The University of Edinburgh, Appleton Tower, Crichton Street, Edinburgh, EH8 9LE UK
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20
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Atamna H. Heme, iron, and the mitochondrial decay of ageing. Ageing Res Rev 2004; 3:303-18. [PMID: 15231238 DOI: 10.1016/j.arr.2004.02.002] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2004] [Accepted: 02/04/2004] [Indexed: 01/04/2023]
Abstract
Heme, the major functional form of iron, is synthesized in the mitochondria. Although disturbed heme metabolism causes mitochondrial decay, oxidative stress, and iron accumulation, all of which are hallmarks of ageing, heme has been little studied in nutritional deficiency, in ageing, or age-related disorders such as Alzheimer's disease (AD). Biosynthesis of heme requires Vitamin B(6), riboflavin, biotin, pantothenic acid, and lipoic acid and the minerals zinc, iron, and copper, micronutrients are essential for the production of succinyl-CoA, the precursor for porphyrins, by the TCA (Krebs) cycle. Only a small fraction of the porphyrins synthesized from succinyl-CoA are converted to heme, the rest are excreted out of the body together with the degradation products of heme (e.g. bilirubin). Therefore, the heme biosynthetic pathway causes a net loss of succinyl-CoA from the TCA cycle. The mitochondrial pool of succinyl-CoA may limit heme biosynthesis in deficiencies for micronutrients (e.g. iron or biotin deficiency). Ageing and AD are also associated with hypometabolism, increase in heme oxygenase-1, loss of complex IV, and iron accumulation. Heme is a common denominator for all these changes, suggesting that heme metabolism maybe altered in age-related disorders. Heme can also be a prooxidant: it converts less reactive oxidants to highly reactive free radicals. Free heme has high affinity for different cell structures (protein, membranes, and DNA), triggering site-directed oxidative damage. This review discusses heme metabolism as related to metabolic changes seen in ageing and age-related disorders and highlights the possible role in iron deficiency.
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Affiliation(s)
- Hani Atamna
- Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609-1673, USA.
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21
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Ren Y, Schulz H. Metabolic functions of the two pathways of oleate beta-oxidation double bond metabolism during the beta-oxidation of oleic acid in rat heart mitochondria. J Biol Chem 2003; 278:111-6. [PMID: 12397064 DOI: 10.1074/jbc.m209261200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Unsaturated fatty acids with odd-numbered double bonds, e.g. oleic acid, can be degraded by beta-oxidation via the isomerase-dependent pathway or the reductase-dependent pathway that differ with respect to the metabolism of the double bond. In an attempt to elucidate the metabolic functions of the two pathways and to determine their contributions to the beta-oxidation of unsaturated fatty acids, the degradation of 2-trans,5-cis-tetradecadienoyl-CoA, a metabolite of oleic acid, was studied with rat heart mitochondria. Kinetic measurements of metabolite and cofactor formation demonstrated that more than 80% of oleate beta-oxidation occurs via the classical isomerase-dependent pathway whereas the more recently discovered reductase-dependent pathway is the minor pathway. However, the reductase-dependent pathway is indispensable for the degradation of 3,5-cis-tetradecadienoyl-CoA, which is formed from 2-trans,5-cis-tetradecadienoyl-CoA by delta(3),delta(2)-enoyl-CoA isomerase, the auxiliary enzyme that is essential for the operation of the major pathway of oleate beta-oxidation. The degradation of 3,5-cis-tetradecadienoyl-CoA is limited by the capacity of 2,4-dienoyl-CoA reductase to reduce 2-trans,4-trans-tetradecadienoyl-CoA, which is rapidly formed from its 3,5 isomer by delta(3,5),delta(2,4)-dienoyl-CoA isomerase. It is concluded that both pathways are essential for the degradation of unsaturated fatty acids with odd-numbered double bonds inasmuch as the isomerase-dependent pathway facilitates the major flux through beta-oxidation and the reductase-dependent pathway prevents the accumulation of an otherwise undegradable metabolite.
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Affiliation(s)
- Ying Ren
- Department of Chemistry, City College and Graduate School of the City University of New York, New York, New York 10031, USA
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22
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Comte B, Vincent G, Bouchard B, Benderdour M, Des Rosiers C. Reverse flux through cardiac NADP(+)-isocitrate dehydrogenase under normoxia and ischemia. Am J Physiol Heart Circ Physiol 2002; 283:H1505-14. [PMID: 12234803 DOI: 10.1152/ajpheart.00287.2002] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Little is known about the role of mitochondrial NADP(+)-isocitrate dehydrogenase (NADP(+)-ICDH) in the heart, where this enzyme shows its highest expression and activity. We tested the hypothesis that in the heart, NADP(+)-ICDH operates in the reverse direction of the citric acid cycle (CAC) and thereby may contribute to the fine regulation of CAC activity (Sazanov and Jackson, FEBS Lett 344: 109-116, 1994). We documented a reverse flux through this enzyme in rat hearts perfused with the medium-chain fatty acid octanoate using [U-(13)C(5)]glutamate and mass isotopomer analysis of tissue citrate (Comte et al., J Biol Chem 272: 26117-26124, 1997). In this study, we assessed the significance of our previous finding by perfusing hearts with long-chain fatty acids and tested the effects of changes in O(2) supply. We showed that under all of these conditions citrate was enriched in an isotopomer containing five (13)C atoms. This isotopomer can only be explained by substrate flux through reversal of the NADP(+)-ICDH reaction, which is evaluated at 3-7% of flux through citrate synthase. Small variations in reversal fluxes induced by low-flow ischemia that mimicked hibernation occurred despite major changes in contractile function and O(2) consumption of the heart as well as citrate and succinate release rates and tissue levels. Our data show a reverse flux through NADP(+)-ICDH and support its hypothesized role in the fine regulation of CAC activity in the normoxic and O(2)-deprived heart.
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Affiliation(s)
- Blandine Comte
- Department of Nutrition, University of Montreal, Quebec H3C 3J7, Canada
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23
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Abstract
The control of mitochondrial beta-oxidation, including the delivery of acyl moieties from the plasma membrane to the mitochondrion, is reviewed. Control of beta-oxidation flux appears to be largely at the level of entry of acyl groups to mitochondria, but is also dependent on substrate supply. CPTI has much of the control of hepatic beta-oxidation flux, and probably exerts high control in intact muscle because of the high concentration of malonyl-CoA in vivo. beta-Oxidation flux can also be controlled by the redox state of NAD/NADH and ETF/ETFH(2). Control by [acetyl-CoA]/[CoASH] may also be significant, but it is probably via export of acyl groups by carnitine acylcarnitine translocase and CPT II rather than via accumulation of 3-ketoacyl-CoA esters. The sharing of control between CPTI and other enzymes allows for flexible regulation of metabolism and the ability to rapidly adapt beta-oxidation flux to differing requirements in different tissues.
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Affiliation(s)
- Simon Eaton
- Surgery Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK.
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24
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Eaton S, Middleton B, Sherratt HS, Pourfarzam M, Quant PA, Bartlett K. Control of mitochondrial beta-oxidation at the levels of [NAD+]/[NADH] and CoA acylation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 466:145-54. [PMID: 10709638 DOI: 10.1007/0-306-46818-2_16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- S Eaton
- Unit of Paediatric Surgery, University College London Medical School.
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25
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Howlett RA, Willis WT. Fiber-type-related differences in the enzymes of a proposed substrate cycle. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1363:224-30. [PMID: 9518625 DOI: 10.1016/s0005-2728(98)00002-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A substrate cycle between citric acid cycle (CAC) intermediates isocitrate and 2-oxoglutarate, involving NAD+- and NADP+-linked isocitrate dehydrogenase (NAD-IDH and NADP-IDH, respectively) and mitochondrial transhydrogenase (H+-Thase), has recently been proposed. This cycle has been hypothesized to enhance mitochondrial respiratory control by increasing the sensitivity of NAD-IDH to its modulators and allowing for enhanced increases in flux through this step of the CAC during periods of increased ATP demand. The activities of the enzymes comprising the substrate cycle: NAD-IDH, forward and reverse NADP-IDH, and forward and reverse H+-Thase, along with the activity of a marker of mitochondrial content, citrate synthase (CS) were measured in mitochondria isolated from rabbit Type I and Type IIb muscles and in whole muscle homogenates, representing the various fiber types, from rats. In isolated rabbit muscle mitochondria, NAD-IDH had significantly higher (1.6 x ) activity in white muscle while forward NADP-IDH, forward and reverse H+-Thase, and CS all had significantly higher (1.2-1.6 x ) activities in red muscle. There was no difference in reverse NADP-IDH between fiber types. Similarly, in rat whole muscle enzyme activities normalized to CS, NAD-IDH had significantly higher activity in fast-twitch glycolytic (FG) fibers, while forward NADP-IDH and forward H+-Thase had significantly higher activities in slow-twitch oxidative (SO) fibers. These results suggest that differences in the activities of the substrate cycle enzymes between skeletal muscle fiber types could contribute to differences in respiratory control due to differential cycling rates and/or loci of control.
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Affiliation(s)
- R A Howlett
- Exercise and Sport Research Institute, Dept. of Exercise Science and Physical Education, Arizona State University, Tempe, AZ, 85287-0404, USA.
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26
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Yao KW, Schulz H. Intermediate channeling on the trifunctional beta-oxidation complex from pig heart mitochondria. J Biol Chem 1996; 271:17816-20. [PMID: 8663442 DOI: 10.1074/jbc.271.30.17816] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The kinetic properties of the purified trifunctional beta-oxidation complex (TOC) from pig heart mitochondria were analyzed with the aim of elucidating the functional consequence of having three sequentially acting enzymes of beta-oxidation associated in one complex. The kinetic parameters of TOC and of the component enzymes of TOC, long-chain enoyl-CoA hydratase, long-chain 3-hydroxyacyl-CoA dehydrogenase, and long-chain 3-ketoacyl-CoA thiolase, were determined with substrates having acyl chains with 16 carbon atoms. Quantification by high performance liquid chromatography of intermediates formed during the degradation of 2-trans-hexadecanoyl-CoA to myristoyl-CoA and acetyl-CoA by TOC revealed the accumulation of 3-hydroxyhexadecanoyl-CoA, whereas 3-ketohexadecanoyl-CoA was undetectable. The observed rates of NADH and acetyl-CoA formation were higher than the theoretical rates calculated by use of the kinetic parameters and measured concentrations of intermediates. When the sequence of reactions catalyzed by TOC was inhibited by acetyl-CoA, the steady-state concentration of the 3-hydroxyacyl-CoA intermediate was not affected, whereas a small amount of 3-ketohexadecanoyl-CoA was detected. The differences between observed and predicted reaction rates and between measured and expected concentrations of intermediates are best explained by the operation of a channeling mechanism. As a consequence of intermediate channeling between the active sites on the complex, more coenzyme A is available in the mitochondrial matrix and metabolites like 3-ketoacyl-CoA thioesters, which are strong inhibitors of several beta-oxidation enzymes, do not accumulate.
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Affiliation(s)
- K W Yao
- Department of Chemistry, City College, City University of New York, New York, New York 10031, USA
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27
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Reversibility of the mitochondrial isocitrate dehydrogenase reaction in the perfused rat liver. Evidence from isotopomer analysis of citric acid cycle intermediates. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)46965-7] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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28
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Sazanov LA, Jackson JB. Proton-translocating transhydrogenase and NAD- and NADP-linked isocitrate dehydrogenases operate in a substrate cycle which contributes to fine regulation of the tricarboxylic acid cycle activity in mitochondria. FEBS Lett 1994; 344:109-16. [PMID: 8187868 DOI: 10.1016/0014-5793(94)00370-x] [Citation(s) in RCA: 160] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
H(+)-transhydrogenase (H(+)-Thase) and NADP-linked isocitrate dehydrogenase (NADP-ICDH) are very active in animal mitochondria but their physiological function is only poorly understood. This is especially so in the case of the heart and muscle, where there are no major consumers of NADPH. We propose here that H(+)-Thase and NADP-ICDH have a combined function in the fine regulation of the activity of the tricarboxylic acid (TCA) cycle, providing enhanced sensitivity to changes in energy demand. This is achieved through cycling of substrates by NAD-linked ICDH, NADP-linked ICDH and H(+)-Thase. It is proposed that NAD-ICDH operates in the forward direction of the TCA cycle, but NADP-ICDH is driven in reverse by elevated levels of NADPH resulting from the action of the transmembrane proton electrochemical potential gradient (delta p) on H(+)-Thase. This has the effect of increasing the sensitivity to allosteric modifiers of NAD-ICDH (NADH, ADP, ATP, Ca2+ etc), potentially giving rise to large changes in the net flux from iso-citrate to alpha-ketoglutarate. Furthermore, changes in the level of delta p resulting from changes in the demand for ATP would, via H(+)-Thase, shift the redox state of the NADP pool and this, in turn, would lead to a change in the rate of the reaction catalysed by NADP-ICDH and hence to an additional and complementary effect on the net metabolic flux from isocitrate to alpha-ketoglutarate. Other consequences of this substrate cycle are, (i) the production of heat at the expense of delta p, which may contribute to thermoregulation in the animal, and (ii) an increased rate of dissipation of delta p (leak).
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Affiliation(s)
- L A Sazanov
- School of Biochemistry, University of Birmingham, UK
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29
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Abstract
The activation of intramitochondrial dehydrogenases by Ca2+ provides a link between the intensity of work performance by a tissue and the activity of pyruvate dehydrogenase and the tricarboxylate cycle, and hence the rate of ATP production by the mitochondria. Several aspects of this model of the control of oxidative phosphorylation are examined in this article, with particular emphasis on mitochondrial functioning in situ in cardiac myocytes and in the intact heart. Recent use of the fluorescent Ca2+ chelating agents indo-1 and fura-2 has allowed a more quantitative description of the dependence of dehydrogenase activity upon concentration of free intramitochondrial Ca2+, in experiments with isolated mitochondria. Further, a novel technique developed by Miyata et al. has allowed description of free intramitochondrial Ca2+ within a single cardiac myocyte, and the conclusion that this parameter changes in response to electrical excitation of the cell over a range which would be expected to give substantial modulation of dehydrogenase activity.
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Affiliation(s)
- R G Hansford
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, Maryland 21224
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30
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Wang HY, Baxter CF, Schulz H. Regulation of fatty acid beta-oxidation in rat heart mitochondria. Arch Biochem Biophys 1991; 289:274-80. [PMID: 1898072 DOI: 10.1016/0003-9861(91)90472-u] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In an attempt to elucidate the mechanism by which the rate of fatty acid oxidation is tuned to the energy demand of the heart, the effects of changing intramitochondrial ratios of [acetyl-CoA]/[CoASH] and [NADH]/[NAD+] on the rate of beta-oxidation were studied. When 10 mM L-carnitine was added to coupled rat heart mitochondria to lower the ratio of [acetyl-CoA]/[CoASH], the rate of palmitoylcarnitine beta-oxidation, as measured by the formation of acid-soluble products, was stimulated more than fourfold at state 4 respiration while beta-oxidation at state 3 respiration was hardly affected. Neither oxaloacetate nor acetoacetate, added to mitochondria to lower the [NADH]/[NAD+] ratio, stimulated beta-oxidation. Rates of respiration at states 3 and 4 were unchanged by additions of L-carnitine, oxaloacetate, or acetoacetate. Determinations of intramitochondrial ratios of [acetyl-CoA]/[CoASH] by high performance liquid chromatography yielded values close to 10 for palmitoylcarnitine-supported respiration at state 4 and 2.5 at state 3 respiration. Addition of 10 mM L-carnitine caused a dramatic decrease of these ratios to less than 0.2 at both respiration states. Studies with purified or partially purified enzymes revealed strong inhibitions of 3-ketoacyl-CoA thiolase by acetyl-CoA and of L-3-hydroxyacyl-CoA dehydrogenase by NADH. Moreover, the activity of 3-ketoacyl-CoA thiolase at concentrations of acetyl-CoA and CoASH prevailing at state 3 respiration was 4 times higher than its activity in the presence of acetyl-CoA and CoASH observed at state 4. Altogether, this study leads to the conclusion that the rate of beta-oxidation in heart can be regulated by the intramitochondrial ratio of [acetyl-CoA]/[CoASH] which reflects the energy demand of the tissue. The thiolytic cleavage catalyzed by 3-ketoacyl-CoA thiolase may be the site at which beta-oxidation is controlled by the [acetyl-CoA]/[CoASH] ratio.
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Affiliation(s)
- H Y Wang
- Department of Chemistry, City College of the City University of New York, New York 10031
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31
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Yadav RN. Isocitrate dehydrogenase activity and its regulation by estradiol in tissues of rats of various ages. Cell Biochem Funct 1988; 6:197-202. [PMID: 3409480 DOI: 10.1002/cbf.290060308] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The activity and hormonal regulation of NAD- and NADP-linked isocitrate dehydrogenase (EC.1.1.1.41 and EC.1.1.1.42, respectively) in the brain, liver and kidney cortex of female rats of various ages was investigated. The activity of NAD-ICDH of brain was greater than extramitochondrial (-c) or intramitochondrial (-m) NADP-ICDH. In contrast, liver c-NADP-ICDH was much higher than NAD- or m-NADP-ICDH, whereas in kidney cortex the activity of m-NADP-ICDH is dominant over both NAD- and c-NADP-ICDH in all the age group of rats studied. The activity of the NAD-ICDH of brain and all the enzymes of liver and kidney cortex increases until adulthood (33-weeks) and decreases thereafter in old rats (85-weeks). In brain c-NADP-ICDH was much higher in immature (6-weeks) rats and decreases with increasing age of the animal, whereas m-NADP-ICDH showed no significant change with the age of the rats. Bilateral ovariectomy decreases the level of all the three forms of enzyme in all the tissues of 6-, 13- and 33-week rats but failed to show any significant effect in 85-week old rats. Exogenous administration of estradiol induces all the three forms of enzyme in all the tissues of ovariectomized rats. The degree of response is tissue- and age-specific.
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Affiliation(s)
- R N Yadav
- Department of Life Sciences, Dibrugarh University, Assam, India
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Storey KB, Fields JH. NAD(+)-linked isocitrate dehydrogenase in fish tissues. FISH PHYSIOLOGY AND BIOCHEMISTRY 1988; 5:1-8. [PMID: 24226466 DOI: 10.1007/bf01874723] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
NAD(+)-linked isocitrate dehydrogenase was found in the brain, heart, gills, kidney, liver and muscle of trout, and in the liver and muscle of eel. A complex homogenization buffer containing 1 mM ADP, 5 mM MgSO4, 5 mM citrate and 40% glycerol is required for retrieval of significant amounts of stable enzyme. The highest activities were found in brain of trout and the lowest in white muscle of trout and eel. The enzyme was partially purified from frozen trout heart to a final activity of 0.04 μM/min/mg protein, and the kinetic properties of this partially purified enzyme were studied. The enzyme requires either Mn(2+) or Mg(2+) for activity, higher activities being observed with Mn(2+). Saturation kinetics for DL-isocitrate were sigmoidal, apparent S0·5=8.2±0.6 mM and nH=1.8±0.2, in the absence of ADP, changing to hyperbolic, apparent S0·5=1.4±0.3 mM and nH=1.0, with 1 mM ADP added. Citrate and Ca(2+) were found to activate the enzyme to a small extent. NADH strongly inhibited the enzyme, I50=3.7±0.5 μM. ATP was also found to be an inhibitor, I50=7.2±1.4 mM. These properties are consistent with the role of the enzyme as a major control site of the tricarboxylic acid cycle.
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Affiliation(s)
- K B Storey
- Institute of Biochemistry, Carleton University, K1S 5B6, Ottawa, Ontario, Canada
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Lysiak W, Lilly K, DiLisa F, Toth PP, Bieber LL. Quantitation of the effect of L-carnitine on the levels of acid-soluble short-chain acyl-CoA and CoASH in rat heart and liver mitochondria. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)57279-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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34
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Dry IB, Wiskich JT. 2-Oxoglutarate dehydrogenase and pyruvate dehydrogenase activities in plant mitochondria: interaction via a common coenzyme a pool. Arch Biochem Biophys 1987; 257:92-9. [PMID: 3631965 DOI: 10.1016/0003-9861(87)90546-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
2-Oxoglutarate (2-OG)-dependent O2 uptake by washed or purified turnip (Brassica rapa L.) and pea (Pisum sativum L. cv. Massey Gem) leaf mitochondria, in the presence of malonate, was inhibited between 65 and 90% by micromolar levels of pyruvate. The inhibition was not observed in the absence of malonate and was reversed by alpha-cyano-4-hydroxycinnamic acid. The inhibition was also reversed by oxaloacetate or by malate, but not by any other tricarboxylic acid cycle intermediates. The stimulation of O2 uptake by oxaloacetate was half maximal at 8-9 microM and was transient, indicating its action was not mediated through the complete metabolic removal of pyruvate. Pyruvate had not effect on 2-OG oxidation under conditions in which pyruvate dehydrogenase was not active, indicating that pyruvate metabolism, rather than pyruvate itself, was responsible for producing the inhibition of 2-OG oxidation. Similar results were obtained with detergent-treated mitochondrial extracts with the exception that the inhibition of 2-OG oxidation by pyruvate could also be reversed by coenzyme A. The results suggest that pyruvate inhibits 2-oxoglutarate oxidation, in intact plant mitochondria, by sequestering intramitochondrial CoA as acetyl-CoA and, in the absence of citrate synthase activity, reduces the amount of free coenzyme A available for 2-oxoglutarate dehydrogenase. These results indicate that pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase share a common CoA pool within plant mitochondria and that the turnover of the acyl-CoA product of one enzyme will dramatically influence the activity of the other.
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Marcillat O, Goldschmidt D, Eichenberger D, Vial C. Only one of the two interconvertible forms of mitochondrial creatine kinase binds to heart mitoplasts. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 890:233-41. [PMID: 3801463 DOI: 10.1016/0005-2728(87)90024-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
When analyzed by cellulose acetate electrophoresis, solubilized pig or rabbit heart mitochondrial creatine kinase is shown to exist under two distinct forms. The less cathodic one (form 1) is a dimer and the other having a higher cathodic mobility (form 2) has a molecular weight of about 350,000. The latter form can be converted into the former by incubation at alkaline pH or when the enzyme forms a reactive or an abortive complex with its substrates. This conversion is a reversible phenomenon and is not due to proteolysis. When rabbit heart mitoplasts are treated with the creatine kinase releasing agents, the enzyme is always solubilized as its form 2 and conversion to form 1, when it occurs, always take place after solubilization. Form 2 is also the only form which can be bound to pig or rabbit mitoplasts. Thus form 2 may be the actual form associated with heart mitochondria in vivo.
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Gabriel JL, Zervos PR, Plaut GW. Activity of purified NAD-specific isocitrate dehydrogenase at modulator and substrate concentrations approximating conditions in mitochondria. Metabolism 1986; 35:661-7. [PMID: 3724458 DOI: 10.1016/0026-0495(86)90175-7] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The kinetic parameters of NAD-specific isocitrate dehydrogenase from bovine heart were examined at levels of substrates and effectors approximating the concentrations reported for isolated intact heart mitochondria in different respiratory states. The effect of changing ADP/ATP ratios (with total adenine nucleotides constant at 8 mmol/L) on enzyme activity was measured at constant concentrations of the substrates magnesium D-isocitrate (0.10 mmol/L) and NAD+ (3.0 mmol/L), the positive effector magnesium citrate (1.0 mmol/L) and the negative effector NADPH (1.5 mmol/L) at pH 7.4. Enzyme activity increased with increasing ADP/ATP ratios as a result of activation by rising ADP concentrations and not due to decreasing inhibition by falling levels of ATP. Increasing ADP decreased the inhibition by NADPH, and this effect was enhanced by magnesium citrate and by free Ca2+. In incubation media containing all of the above effectors, the S0.5 for enhancement of activity by free Ca2+ was 10 to 20 mumol/L at ratios of total ADP/total ATP between 2.0 and 0.1. This value is in the range of intramitochondrial concentrations of free Ca2+,1 but it is appreciably larger than S0.5 of Ca2+ (0.6 to 1 mumol/L) for the enhancement of ADP activation, which was determined in the absence of other effectors. When both the NAD+/NADH and the ADP/ATP ratios were decreased, a further decline in activity was found. The effect of the decreasing NAD+/NADH ratio was due to inhibition by NADH (apparent I0.5 = 0.23 +/- 0.03 mmol/L) since NAD+ was saturating over the range examined.
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Thurston JH, Hauhart RE, Schiro JA. Beta-hydroxybutyrate reverses insulin-induced hypoglycemic coma in suckling-weanling mice despite low blood and brain glucose levels. Metab Brain Dis 1986; 1:63-82. [PMID: 3334063 DOI: 10.1007/bf00998478] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In normal suckling-weanling mice, DL-beta-hydroxybutyrate (30 mmol/kg ip) stimulated insulin secretion and reduced plasma glucose levels. In the brains of these animals, glucose levels were tripled due to a reduced rate of glucose utilization (determined by deoxyglucose phosphorylation). Other metabolite changes were compatible with inhibition of hexokinase, phosphofructokinase, glyceraldehyde-P-dehydrogenase, and pyruvate dehydrogenase activities. In contrast to the decrease in cerebral glycolysis, metabolite changes were compatible with an increase in the Krebs citric acid metabolic flux. The brain energy charge was also elevated. While it is generally believed that ketone bodies cannot sustain normal brain metabolism and function in the absence of glucose, DL-beta-hydroxybutyrate (20 or 30 mmol/kg ip) reversed insulin (100 U/kg sc)-induced hypoglycemia despite the persistence of a critically reduced plasma glucose concentration and near-zero brain glucose levels. Metabolic correlates of possible significance in the behavioral recovery from coma were reductions of the elevated levels of brain aspartate to below normal and ammonia levels to normal. Levels of acetyl CoA were unchanged both before and after treatment with beta-hydroxybutyrate.
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Affiliation(s)
- J H Thurston
- Washington University School of Medicine, Department of Pediatrics, Children's Hospital, St. Louis, Missouri 63110
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Abstract
The heart muscle has proved to be a practical model for studying respiratory control in intact tissues. It also demonstrates that control at the level of the respiratory chain is augmented by metabolic control at the substrate level as exemplified by the very narrow range of changes in the redox state of the mitochondrial NADH/NAD couple even during extensive changes in ATP and oxygen consumption. The behaviour of mitochondria when isolated can largely be duplicated in the intact myocardium. Moreover, the high intracellular concentrations of enzymes, coenzymes and adenine nucleotides create conditions of high reaction rates, enabling the formation of a near equilibrium network of certain main pathways. This equilibrium network in connection with metabolic regulation of the hydrogen pressure upon the matrix NADH/NAD pool is a prerequisite for the regulation of cellular respiration at a high efficiency of energy transfer. Experimentation on the intact myocardium also seems to be capable of resolving some of the uncertainties about prevailing mechanisms for the regulation of cellular respiration.
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Toth PP, Ferguson-Miller SM, Suelter CH. Isolation of highly coupled heart mitochondria in high yield using a bacterial collagenase. Methods Enzymol 1986; 125:16-27. [PMID: 3012258 DOI: 10.1016/s0076-6879(86)25004-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Aubert-Foucher E, Font B, Gautheron DC. Modified properties of hexokinase from heart mitochondria prepared using proteolytic enzyme. Mol Cell Biochem 1985; 67:111-8. [PMID: 3900691 DOI: 10.1007/bf02370169] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Isolation of muscle mitochondria is made easier by using proteolytic treatment of the tissue before homogenization. Normally, the proteolytic enzyme is discarded with the supernatant of the first centrifugation. However, our results show that a fraction of enzyme activity remains associated with mitochondria. As shown in experiments described in this paper, mitochondrial hexokinase from tissue treated or not with the proteolytic enzyme exhibits similar properties except that the solubilized enzyme from protease treated tissue is no longer able to rebind to mitochondrial membrane. This modification of the binding ability of the enzyme results from a partial hydrolysis of hexokinase during solubilization experiments by the proteolytic enzyme. Since, as pointed out here, proteolytic enzyme can remain associated with mitochondria, [either absorbed on mitochondrial membrane or included in the mitochondrial pellet] its use for the isolation of muscle mitochondria should be avoided.
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Gabriel JL, Milner R, Plaut GW. Inhibition and activation of bovine heart NAD-specific isocitrate dehydrogenase by ATP. Arch Biochem Biophys 1985; 240:128-34. [PMID: 2990340 DOI: 10.1016/0003-9861(85)90015-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In the absence of added calcium, inhibition of NAD-specific isocitrate dehydrogenase by ATP occurred without ADP (I0.5 = 1.8 mM) and with 0.2 mM ADP3- (I0.5 = 1.0 mM) at subsaturating substrate concentrations at pH 7.4. Inhibition by ATP was competitive with NAD+ in the presence and absence of ADP and was not reversed by magnesium citrate. No reversal of ATP inhibition by free Ca2+ was observed in the presence of ADP (0.2 mM). However, when ADP was absent, increasing Ca2+ first caused progressive reversal of ATP inhibition followed by activation by ATP. Without ADP, the S0.5 for calcium activation was 80-140 microM at ATP concentrations between 0.6 and 3.0 mM. The S0.5 for ATP activation, in the absence of ADP, was 1.1 and 2.1 microM when free Ca2+ was held constant at 0.1 and 1.0 mM, respectively. As in activation by ADP, ATP decreased the S0.5 for magnesium isocitrate without affecting V. However, in contrast to ADP, the activation by ATP occurred without lowering the Hill coefficient for the substrate. GDP activated the enzyme at relatively high concentrations of Ca2+ but not without added Ca2+.
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42
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Sabbagh E, Cuebas D, Schulz H. 3-Mercaptopropionic acid, a potent inhibitor of fatty acid oxidation in rat heart mitochondria. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)39613-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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43
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Yadav RN. Regulation of NAD- and NADP-linked isocitrate dehydrogenase by thyroxine in the brain and liver of female rats of various ages. BIOCHEMICAL MEDICINE 1985; 33:312-9. [PMID: 4015631 DOI: 10.1016/0006-2944(85)90005-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The specific activity of NAD- and NADP-linked isocitrate dehydrogenase and their regulation by thyroxine in the brain and liver of female rats of various ages were studied with the ultimate goal of better understanding the decreased physiological functioning of the brain and liver during old age. Both thyroidectomy and thyroxine treatment have differential age-dependent effects on the activities of these enzymes in both tissues. The activity of NAD-ICDH decreases whereas both cytoplasmic and mitochondrial NADP-ICDH increase simultaneously following thyroidectomy. Thyroxine administration induces NAD-ICDH and depresses NADP-ICDH. The degree of induction and/or repression is lowest in old rats. These effects of thyroxine are actinomycin D sensitive in both the tissues of rats.
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Kuo TH, Giacomelli F, Wiener J. Oxidative metabolism of Polytron versus Nagarse mitochondria in hearts of genetically diabetic mice. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 806:9-15. [PMID: 3967008 DOI: 10.1016/0005-2728(85)90076-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
We have shown previously that heart mitochondria obtained by the Nagarse method from genetically diabetic mice (C57BL/KsJ db/db) exhibit a defect in oxidizing NAD+-linked substrates (Kuo, T.H., Moore, K.H., Giacomelli, F. and Wiener, J. (1983) Diabetes 32, 781-787). In this study, the oxidative phosphorylation characteristics of cardiac mitochondria isolated by the Polytron method were compared with that of Nagarse mitochondria. Evidence is presented here that in the diabetic heart both Nagarse and Polytron mitochondria have defective pyruvate oxidation, whereas only the former exhibit impaired fatty acid oxidation. Assay of two rate-limiting beta-oxidation enzymes, namely beta-hydroxyacyl-CoA dehydrogenase and beta-ketothiolase, indicates no alteration in specific activities from diabetic mice vs. controls. The data suggest that two populations of mitochondria are present in myocardium and that the defective oxidative metabolism in the cardiac mitochondria of db/db mice may be linked to deficiencies in total NAD + NADH content.
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Aubert-Foucher E, Font B, Gautheron DC. Rabbit heart mitochondrial hexokinase: solubilization and general properties. Arch Biochem Biophys 1984; 232:391-9. [PMID: 6742859 DOI: 10.1016/0003-9861(84)90554-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
In rabbit heart, results show that two isoenzymes of hexokinase (HK) are present. The enzymatic activity associated with mitochondria consists of only one isoenzyme; according to its electrophoretic mobility and its apparent Km for glucose (0.065 mM), it has been identified as type I isoenzyme. The bound HK I exhibits a lower apparent Km for ATPMg than the solubilized enzyme, whereas the apparent Km for glucose is the same for bound and solubilized HK. Detailed studies have been performed to investigate the interactions which take place between the enzyme and the mitochondrial membrane. Neutral salts efficiently solubilize the bound enzyme. Digitonin induces only a partial release of the enzyme bound to mitochondria; this result could be explained by the existence of contacts between the outer and the inner mitochondrial membranes [C. R. Hackenbrock (1968) Proc. Natl. Acad. Sci. USA 61, 598-605]. Furthermore, low concentrations (0.1 mM) of glucose 6-phosphate (G6P) or ATP4- specifically solubilize hexokinase. The solubilizing effect of G6P and ATP4-, which are potent inhibitors of the enzyme, can be prevented by incubation of mitochondria with Pi or Mg2+. In addition, enzyme solubilization by G6P can be reversed by Mg2+ only when the proteolytic treatment of the heart homogenate is omitted during the course of the isolation of mitochondria. These results concerning the interaction of rabbit heart hexokinase with the outer mitochondrial membrane agree with the schematic model proposed by Wilson [(1982) Biophys. J. 37, 18-19] for the brain enzyme. This model involves the existence of two kinds of interactions between HK and mitochondria; a very specific one with the hexokinase-binding protein of the outer mitochondrial membrane, which is suppressed by glucose 6-phosphate, and a less specific, cation-mediated one.
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Gabriel JL, Plaut GW. Inhibition of bovine heart NAD-specific isocitrate dehydrogenase by reduced pyridine nucleotides: modulation of inhibition by ADP, NAD+, Ca2+, citrate, and isocitrate. Biochemistry 1984; 23:2773-8. [PMID: 6466615 DOI: 10.1021/bi00307a037] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The activity of NAD-dependent isocitrate dehydrogenase from bovine heart was inhibited by NADH (apparent Ki about 4.3 microM) and NADPH (Ki about 9.8 microM) at subsaturating substrate concentrations at pH 7.4. The inhibition by NADH or NADPH was reversed competitively by magnesium isocitrate in the presence of ADP, but not without ADP. Reversal of inhibition by NADH or NADPH with respect to NAD+ was competitive or of the linear mixed type depending on whether ADP was absent or present. ADP3- (0.2 mM) increased the Ki(app) for NADPH from 9.8 to 27.1 microM; further addition of Ca2+ (0.2 mM) raised the Ki(app) to 127 microM. For the modification of NADPH inhibition by ADP, S0.5 for Ca2+ was approximately 48 microM. This compares to the Km for Ca2+ of 0.3-1 microM for the activation of the enzyme without NADPH [Denton, R. M., Richards, D. A., & Chin, J. G. (1978) Biochem. J. 176, 899-906; Aogaichi, T., Evans, J., Gabriel, J., & Plaut, G. W. E. (1980) Arch. Biochem. Biophys. 204, 350-360]. ADP did not affect the Ki for NADH. Magnesium citrate, which was about 100-fold more effective as a positive modifier of the enzyme with ADP than without ADP [Gabriel, J. L., & Plaut, G. W. E. (1983) Fed. Proc., Fed. Am. Soc. Exp. Biol. 42, 2082], reversed competitively the inhibition by NADPH in the presence of ADP, but not without ADP. Magnesium citrate did not reverse NADH inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)
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Beeckmans S. Some structural and regulatory aspects of citrate synthase. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1984; 16:341-51. [PMID: 6370751 DOI: 10.1016/0020-711x(84)90131-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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48
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49
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Font B, Vial C, Goldschmidt D, Eichenberger D, Gautheron DC. Effects of SH group reagents on creatine kinase interaction with the mitochondrial membrane. Arch Biochem Biophys 1983; 220:541-8. [PMID: 6824338 DOI: 10.1016/0003-9861(83)90445-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Solubilization of the specific mitochondrial isoenzyme of creatine kinase (CKm) from rabbit heart mitochondria by treatment with SH group reagents has been studied. From the various compounds tested only the negatively charged organomercurials are able to induce an extensive solubilization of the enzyme. This effect is fully reversible since the solubilized enzyme readily reassociates with the membrane when the bound organomercurial is removed by treatment of the homogenate by an excess of dithiothreitol. Solubilization by negatively charged organomercurials can be partly prevented by pretreatment of mitochondria with either disulfide or uncharged organomercurials. No clear-cut relationship has been pointed out when the amount of SH titrated by various reagents has been compared with the extent of CKm solubilization. More detailed studies with para-chloromercuribenzoate (pCMB) show that extensive CKm solubilization (about 75%) occurs for pCMB concentration as low as 25 microM, whereas pronounced inhibition of the enzyme is observed only for concentrations greater than 200 microM. By cross-reassociation of enzyme solubilized either by para-hydroxymercuribenzoate (pHMB) or by 20 mM sodium phosphate (NaPi) with mitochondria depleted of CKm by pHMB or by NaPi treatment, SH groups whose titration impedes CKm reassociation with the mitochondrial membrane have been tentatively located on the enzyme. Thus, negatively charged organomercurials, could induce a reversible conformational modification of the enzyme which is no longer able to bind on the inner mitochondrial membrane. Furthermore, our results show that the binding of an excess of mitochondrial CK, which has been previously reported, could reflect unspecific binding since it occurs only on mitoplasts incubated in very hypotonic medium, but not in isotonic medium.
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50
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Ingebretsen OC, Bakken AM, Farstad M. The content of coenzyme A, acetyl-CoA and long-chain acyl-CoA in human blood platelets. Clin Chim Acta 1982; 126:307-13. [PMID: 7151284 DOI: 10.1016/0009-8981(82)90305-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The amounts of coenzyme A (CoASH) and acetyl-CoA in the acid-soluble extract of human blood platelets were quantitated by an isocratic reversed-phase liquid-chromatographic system. The analytical column was Supelcosil LC-18, and the solvent was 220 mmol/l potassium phosphate, pH 4.0, and 120 ml/l methanol. Long-chain acyl-CoA was estimated by the released coenzyme A after an alkaline hydrolysis of the acid-insoluble material of the blood platelets. The median values in platelets from fourteen healthy persons were 30 pmol CoASH/mg platelet protein, 45 pmol acetyl-CoA/mg platelet protein, and 34 pmol long-chain acyl-CoA/mg platelet protein.
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