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Zhang X, Zhang G, Cao L, Zhou W, Tan C, Ma S, Yang J. Two novel SUCLA2 variants cause mitochondrial DNA depletion syndrome, type 5 in two siblings. Front Neurol 2024; 15:1394150. [PMID: 39070054 PMCID: PMC11273780 DOI: 10.3389/fneur.2024.1394150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 07/03/2024] [Indexed: 07/30/2024] Open
Abstract
Mitochondrial DNA depletion syndrome (MDS), characterized by succinate-CoA ligase deficiency and loss of mitochondrial DNA (mtDNA), is caused by specific variants in nuclear genes responsible for mtDNA maintenance. SUCLA2-related mitochondrial DNA depletion syndrome, type 5 (MTDPS-5), presents as a rare, severe early progressive encephalomyopathy. This report investigates a new family exhibiting clinical manifestations of MTDPS-5 and elucidates the genetic basis of this disorder. In two affected siblings, a novel maternally inherited nonsense variant [c.1234C>T (p.Arg412*)] in the SUCLA2 gene and a unique paternally inherited indel variant (g.48569263-48571020del1758insATGA) were identified. Additionally, the siblings exhibited blood mtDNA content lower than 33% compared to age-matched controls. These findings underscore the importance of assessing SUCLA2 variants in patients with severe early progressive encephalomyopathy, even in the absence of methylmalonic aciduria or mtDNA loss, thereby broaden the mutational spectrum of this gene.
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Affiliation(s)
- Xiaohuan Zhang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center of Medical Genetics, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences, Chengdu, China
| | - Guo Zhang
- Dean’s Office, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Li Cao
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center of Medical Genetics, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences, Chengdu, China
| | - Wenjing Zhou
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center of Medical Genetics, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences, Chengdu, China
| | - Chang Tan
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center of Medical Genetics, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences, Chengdu, China
| | - Shi Ma
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center of Medical Genetics, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences, Chengdu, China
| | - Jiyun Yang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center of Medical Genetics, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences, Chengdu, China
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2
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Gaster M, Nehlin JO, Minet AD. Impaired TCA cycle flux in mitochondria in skeletal muscle from type 2 diabetic subjects: marker or maker of the diabetic phenotype? Arch Physiol Biochem 2012; 118:156-89. [PMID: 22385297 DOI: 10.3109/13813455.2012.656653] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The diabetic phenotype is complex, requiring elucidation of key initiating defects. Recent research has shown that diabetic myotubes express a primary reduced tricarboxylic acid (TCA) cycle flux. A reduced TCA cycle flux has also been shown both in insulin resistant offspring of T2D patients and exercising T2D patients in vivo. This review will discuss the latest advances in the understanding of the molecular mechanisms regulating the TCA cycle with focus on possible underlying mechanism which could explain the impaired TCA flux in insulin resistant human skeletal muscle in type 2 diabetes. A reduced TCA is both a marker and a maker of the diabetic phenotype.
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Affiliation(s)
- Michael Gaster
- Laboratory of Molecular Physiology, Department of Pathology, Odense University Hospital, Denmark.
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3
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Kibbey RG, Pongratz RL, Romanelli AJ, Wollheim CB, Cline GW, Shulman GI. Mitochondrial GTP regulates glucose-stimulated insulin secretion. Cell Metab 2007; 5:253-64. [PMID: 17403370 PMCID: PMC1876711 DOI: 10.1016/j.cmet.2007.02.008] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Revised: 12/01/2006] [Accepted: 02/15/2007] [Indexed: 11/15/2022]
Abstract
Nucleotide-specific isoforms of the tricarboxylic acid (TCA) cycle enzyme succinyl-CoA synthetase (SCS) catalyze substrate-level synthesis of mitochondrial GTP (mtGTP) and ATP (mtATP). While mtATP yield from glucose metabolism is coupled with oxidative phosphorylation and can vary, each molecule of glucose metabolized within pancreatic beta cells produces approximately one mtGTP, making mtGTP a potentially important fuel signal. In INS-1 832/13 cells and cultured rat islets, siRNA suppression of the GTP-producing pathway (DeltaSCS-GTP) reduced glucose-stimulated insulin secretion (GSIS) by 50%, while suppression of the ATP-producing isoform (DeltaSCS-ATP) increased GSIS 2-fold. Insulin secretion correlated with increases in cytosolic calcium, but not with changes in NAD(P)H or the ATP/ADP ratio. These data suggest a role for mtGTP in controlling pancreatic GSIS through modulation of mitochondrial metabolism, possibly involving mitochondrial calcium. Furthermore, in light of its tight coupling to TCA oxidation rates, mtGTP production may serve as an important molecular signal of TCA-cycle activity.
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Affiliation(s)
- Richard G. Kibbey
- Department of Internal Medicine, Howard Hughes Medical Institute Yale University School of Medicine New Haven, CT 06520, USA
| | - Rebecca L. Pongratz
- Department of Internal Medicine, Howard Hughes Medical Institute Yale University School of Medicine New Haven, CT 06520, USA
| | - Anthony J. Romanelli
- Department of Internal Medicine, Howard Hughes Medical Institute Yale University School of Medicine New Haven, CT 06520, USA
| | - Claes B. Wollheim
- Department of Cell Physiology and Metabolism University Medical Center CH-1211 Geneva 4, Switzerland
| | - Gary W. Cline
- Department of Internal Medicine, Howard Hughes Medical Institute Yale University School of Medicine New Haven, CT 06520, USA
| | - Gerald I. Shulman
- Department of Internal Medicine, Howard Hughes Medical Institute Yale University School of Medicine New Haven, CT 06520, USA
- Department of Cellular, Howard Hughes Medical Institute Yale University School of Medicine New Haven, CT 06520, USA
- Department of Molecular Physiology, Howard Hughes Medical Institute Yale University School of Medicine New Haven, CT 06520, USA
- *To whom correspondence should be addressed. E-mail:
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4
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Lambeth DO. Reconsideration of the significance of substrate-level phosphorylation in the citric acid cycle*. BIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION : A BIMONTHLY PUBLICATION OF THE INTERNATIONAL UNION OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2006; 34:21-29. [PMID: 21638627 DOI: 10.1002/bmb.2006.49403401021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
For nearly 50 years, students of metabolism in animals have been taught that a substrate-level phosphorylation in the Krebs citric acid cycle produces GTP that subsequently undergoes a transphosphorylation with ADP catalyzed by nucleoside diphosphate kinase. Research in the past decade has revealed that animals also express an ADP-forming succinate-CoA ligase whose activity exceeds that of the GDP-forming enzyme in some tissues. Here I argue that the primary fate of GTP is unlikely to be transphosphorylation with ADP. Rather, two succinate-CoA ligases with different nucleotide specificities have evolved to better integrate and regulate the central metabolic pathways that involve the citric acid cycle. The products of substrate-level phosphorylation, ATP and/or GTP, may represent a pool of nucleotide that has a different phosphorylation potential than the ATP made by oxidative phosphorylation and may be channeled to meet specific needs within mitochondria and the cell. Further research is needed to determine the applicable mechanisms and how they vary in tissues.
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Affiliation(s)
- David O Lambeth
- Department of Biochemistry and Molecular Biology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203-9037.
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5
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Elpeleg O, Miller C, Hershkovitz E, Bitner-Glindzicz M, Bondi-Rubinstein G, Rahman S, Pagnamenta A, Eshhar S, Saada A. Deficiency of the ADP-forming succinyl-CoA synthase activity is associated with encephalomyopathy and mitochondrial DNA depletion. Am J Hum Genet 2005; 76:1081-6. [PMID: 15877282 PMCID: PMC1196446 DOI: 10.1086/430843] [Citation(s) in RCA: 248] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Accepted: 04/07/2005] [Indexed: 11/03/2022] Open
Abstract
The mitochondrial DNA (mtDNA) depletion syndrome is a quantitative defect of mtDNA resulting from dysfunction of one of several nuclear-encoded factors responsible for maintenance of mitochondrial deoxyribonucleoside triphosphate (dNTP) pools or replication of mtDNA. Markedly decreased succinyl-CoA synthetase activity due to a deleterious mutation in SUCLA2, the gene encoding the beta subunit of the ADP-forming succinyl-CoA synthetase ligase, was found in muscle mitochondria of patients with encephalomyopathy and mtDNA depletion. Succinyl-CoA synthetase is invariably in a complex with mitochondrial nucleotide diphosphate kinase; hence, we propose that a defect in the last step of mitochondrial dNTP salvage is a novel cause of the mtDNA depletion syndrome.
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Affiliation(s)
- Orly Elpeleg
- Metabolic Disease Unit, Shaare-Zedek Medical Center, Jerusalem, Israel.
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6
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Fraser ME, James MN, Bridger WA, Wolodko WT. Phosphorylated and dephosphorylated structures of pig heart, GTP-specific succinyl-CoA synthetase. J Mol Biol 2000; 299:1325-39. [PMID: 10873456 DOI: 10.1006/jmbi.2000.3807] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Succinyl-CoA synthetase (SCS) catalyzes the reversible phosphorylation/dephosphorylation reaction:¿¿¿rm succinyl ¿hbox ¿-¿CoA+NDP+P_i¿leftrightarrow succinate+CoA+NTP¿¿where N denotes adenosine or guanosine. In the course of the reaction, an essential histidine residue is transiently phosphorylated. We have crystallized and solved the structure of the GTP-specific isoform of SCS from pig heart (EC 6.2.1.4) in both the dephosphorylated and phosphorylated forms. The structures were refined to 2.1 A resolution. In the dephosphorylated structure, the enzyme is stabilized via coordination of a phosphate ion by the active-site histidine residue and the two "power" helices, one contributed by each subunit of the alphabeta-dimer. Small changes in the conformations of residues at the amino terminus of the power helix contributed by the alpha-subunit allow the enzyme to accommodate either the covalently bound phosphoryl group or the free phosphate ion. Structural comparisons are made between the active sites in these two forms of the enzyme, both of which can occur along the catalytic path. Comparisons are also made with the structure of Escherichia coli SCS. The domain that has been shown to bind ADP in E. coli SCS is more open in the pig heart, GTP-specific SCS structure.
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Affiliation(s)
- M E Fraser
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada N6A 5C1
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7
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Johnson JD, Mehus JG, Tews K, Milavetz BI, Lambeth DO. Genetic evidence for the expression of ATP- and GTP-specific succinyl-CoA synthetases in multicellular eucaryotes. J Biol Chem 1998; 273:27580-6. [PMID: 9765291 DOI: 10.1074/jbc.273.42.27580] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Highly ATP- and GTP-specific isoforms of succinyl-CoA synthetase in pigeon incorporate the same alpha-subunit, but different beta-subunits (Johnson, J. D., Muhonen, W. W., and Lambeth, D. O. (1998) J. Biol. Chem. 273, 27573-27579). The sequences of the mature subunits were determined by methods based on reverse transcription-polymerase chain reaction. The 306-residue mature alpha-subunit in pigeon shows >88% identity to its homologues in pig and rat. The sequences of the mature ATP- and GTP-specific beta-subunits (A-beta and G-beta, respectively) in pigeon are 54% identical. These sequences were used to identify expressed sequence tags for human and mouse that were highly homologous to G-beta and A-beta, respectively. The sequences for mature A-beta and G-beta in mouse and human were completed and verified by polymerase chain reaction. The sequence of A-beta in pig was also obtained. The mammalian A-beta sequences show >89% identity to each other; the G-beta sequences are similarly related. However, pairwise comparisons of the A-beta and G-beta sequences revealed <53% identity. Alignment with two sequences of the beta-subunit in Caenorhabditis elegans suggests that the A-beta and G-beta genes arose by duplication early in the evolution of multicellular eucaryotes. The expression of A-beta is strong in numerous mouse and human tissues, which suggests that ATP-specific succinyl-CoA synthetase also plays an important role in species throughout the animal kingdom.
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Affiliation(s)
- J D Johnson
- Department of Biochemistry and Molecular Biology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, USA
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8
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Johnson JD, Muhonen WW, Lambeth DO. Characterization of the ATP- and GTP-specific succinyl-CoA synthetases in pigeon. The enzymes incorporate the same alpha-subunit. J Biol Chem 1998; 273:27573-9. [PMID: 9765290 DOI: 10.1074/jbc.273.42.27573] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two succinyl-CoA synthetases, one highly specific for GTP/GDP and the other for ATP/ADP, have been purified to homogeneity from pigeon liver and breast muscle. The two enzymes are differentially distributed in pigeon, with only the GTP-specific enzyme detected in liver and the ATP-specific enzyme in breast muscle. Based on assays in the direction of CoA formation, the ratios of GTP-specific to ATP-specific activities in kidney, brain, and heart are approximately 7, 1, and 0.1, respectively. Both enzymes have the characteristic alpha- and beta-subunits found in other succinyl-CoA synthetases. Studies of the alpha-subunit by electrophoresis, mass spectrometry, reversed-phase high performance liquid chromatography, and peptide mapping showed that it was the same in the two enzymes. Characterization of the beta-subunits by the same methods indicated that they were different, with the tryptic peptide maps providing evidence that the beta-subunits likely differ along their entire sequences. Because the two succinyl-CoA synthetases incorporate the same alpha-subunit, the determinants of nucleotide specificity must reside within the beta-subunit. Determination of the apparent Michaelis constants showed that the affinity of the GTP-specific enzyme for GDP is greater than that of the ATP-specific enzyme for ADP (7 versus 250 microM). Rather large differences in apparent Km values were also observed for succinate and phosphate.
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Affiliation(s)
- J D Johnson
- Department of Biochemistry and Molecular Biology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, USA
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9
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Ryan DG, Lin T, Brownie E, Bridger WA, Wolodko WT. Mutually exclusive splicing generates two distinct isoforms of pig heart succinyl-CoA synthetase. J Biol Chem 1997; 272:21151-9. [PMID: 9261120 DOI: 10.1074/jbc.272.34.21151] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We have identified two distinct cDNAs encoding the alpha-subunit of pig heart succinyl-CoA synthetase. The derived amino acid sequence of one of these, PHalpha57, is highly similar to the alpha-subunit of the rat liver precursor enzyme. The second cDNA, PHalpha108, was identical throughout its sequence with PHalpha57 except for a stretch of 108 nucleotides which replaced a 57 nucleotide sequence in PHalpha57. Coexpression of either alpha-subunit cDNA with a common pig heart beta-subunit cDNA produced isozymes with GTP-specific enzyme activity. The enzyme produced by the combination of PHalpha57 and the beta-subunit cDNA resembled the "native" enzyme purified from pig heart tissue. In contrast, the expressed enzyme from the combination with PHalpha108 was clearly distinguishable from the native enzyme by, for example, hydroxyapatite chromatography. Moreover, it was now apparent that this isoform had been observed in previous preparations of the native enzyme, but always in very low amounts and, thus, disregarded. We have shown further that the two mRNA transcripts arise from a single gene and are generated by mutually exclusive splicing. The production of the PHalpha108 message involves the use of a non-canonical splice site pair, AT-AA. Finally, we provide evidence for tissue specific regulation in the splicing of the PHalpha108 message.
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Affiliation(s)
- D G Ryan
- Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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10
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Lahti CJ, d'Oliveira CE, Johnson PJ. Beta-succinyl-coenzyme A synthetase from Trichomonas vaginalis is a soluble hydrogenosomal protein with an amino-terminal sequence that resembles mitochondrial presequences. J Bacteriol 1992; 174:6822-30. [PMID: 1400232 PMCID: PMC207358 DOI: 10.1128/jb.174.21.6822-6830.1992] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We describe studies directed toward understanding the biogenesis and origin of the hydrogenosome, an unusual organelle found exclusively in certain anaerobic eukaryotes that lack mitochondria. Hydrogenosomes are involved in fermentative carbohydrate metabolism and are proposed to have arisen through conversion of mitochondria or via endosymbiosis with an anaerobic bacterium. We cloned a gene encoding the beta subunit of the hydrogenosomal protein succinyl-coenzyme A synthetase (beta-SCS) and isolated the protein from Trichomonas vaginalis. The T. vaginalis beta-SCS gene encodes a protein with a calculated molecular mass of 43,980 Da that has 43% amino acid identity (65% similarity) with beta-SCS from Escherichia coli. The trichomonad protein partitions into the soluble fraction of hydrogenosomes treated with sodium carbonate at high pH, consistent with a matrix localization within the organelle. The protein is encoded by a multigene family composed of at least three members. Amino-terminal sequencing of beta-SCS purified from T. vaginalis hydrogenosomes shows that the mature protein lacks the first nine amino acids encoded in the gene. This apparent amino-terminal leader sequence is strikingly similar to that of another hydrogenosomal protein and to mitochondrial presequences.
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Affiliation(s)
- C J Lahti
- Department of Microbiology and Immunology, University of California, Los Angeles 90024-1747
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11
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Jenkins TM, Gorrell TE, Müller M, Weitzman PD. Hydrogenosomal succinate thiokinase in Tritrichomonas foetus and Trichomonas vaginalis. Biochem Biophys Res Commun 1991; 179:892-6. [PMID: 1898409 DOI: 10.1016/0006-291x(91)91902-o] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Succinate thiokinase displays a diversity of nucleotide specificity and molecular size throughout Nature. Eukaryotes and Gram-positive bacteria possess distinct 'small' (dimeric) thiokinase enzymes which are specific for adenine (ADP) or guanine (GDP) nucleotides, whereas Gram-negative bacteria contain a single 'large' (tetrameric) enzyme which utilizes both nucleotides. Succinate thiokinase activities, both ADP- and GDP-dependent, were shown to be hydrogenosomal in Tritrichomonas foetus and Trichomonas vaginalis. Surprisingly, the 'small' enzyme was found in T. foetus whereas T. vaginalis contained a 'large' enzyme.
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12
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Kadrmas EF, Ray PD, Lambeth DO. Apparent ATP-linked succinate thiokinase activity and its relation to nucleoside diphosphate kinase in mitochondrial matrix preparations from rabbit. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1074:339-46. [PMID: 1653609 DOI: 10.1016/0304-4165(91)90083-s] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The relative abilities of ATP and GTP to support succinyl-CoA synthesis by mitochondrial matrix fractions prepared from rabbit heart and liver mitoplasts were investigated. The activity supported by ATP in rabbit heart preparations was less than 15% of that obtained with GTP, while no ATP-supported activity was observed in rabbit liver preparations. However, the addition of 30 micromolar GDP to matrix fractions from either heart or liver stimulated the ATP-supported activity to 40% of that observed with GTP, and the further addition of bovine liver nucleoside diphosphate kinase in the presence of 8 microM added GDP increased the activity to near that observed with GTP. The specific activity of nucleoside diphosphate kinase assayed directly in mitochondrial matrix from heart was about 15% of the specific activity of ATP-supported succinate thiokinase induced upon adding GDP. Evidence for a complex between nucleoside diphosphate kinase and succinate thiokinase in mitochondrial matrix from rabbit heart was obtained by glycerol density gradient centrifugation. It is proposed that binding of nucleoside diphosphate kinase to succinate thiokinase activates the former enzyme, accounts for the ATP-supported succinyl-CoA synthetase activity observed, and is involved in the channeling of high energy phosphate from GTP produced in the Krebs cycle to the ATP pool.
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Affiliation(s)
- E F Kadrmas
- Department of Biochemistry and Molecular Biology, School of Medicine, University of North Dakota, Grand Forks 58202
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13
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Guidoux R. Acetoacetate and malate effects on succinate and energy production by O2-deprived liver mitochondria supplied with 2-oxoglutarate. Arch Biochem Biophys 1991; 287:397-402. [PMID: 1898011 DOI: 10.1016/0003-9861(91)90495-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Acetoacetate provision to Ca(2+)-loaded liver mitochondria (less than 40 micrograms-ion Ca2+ x g protein-1), supplied with 2 mM Pi and 2-oxoglutarate as substrate, was found to prevent the mitochondrial deenergization and Ca2+ release induced by either rotenone during aerobic incubations or by O2 deprivation. Under the latter condition, the acetoacetate-promoted Ca2+ retention was entirely supported by ATP produced anaerobically at the succinylthiokinase step of the tricarboxylic acid cycle and was therefore abolished by addition of oligomycin. Surprisingly, oligomycin was also found to trigger Ca2+ release in rotenone-inhibited mitochondria in the presence of acetoacetate under aerobic conditions, unless a Pi acceptor was supplied. ADP deprivation at the succinylthiokinase step is likely to be involved. As estimated from rates of succinate production in O2-deprived mitochondria or from respiration rates in rotenone-inhibited mitochondria at supramaximal acetoacetate concentrations (above 1.2 mM) in the presence of a Pi acceptor, ATP production by substrate-level phosphorylation was close to 10 mumol.g protein-1.min-1 and appeared to be limited by rates of ketone body transport across the inner membrane. The rates of anaerobic energy production obtained by coupling 2-oxoglutarate oxidation to acetoacetate reduction were markedly higher than those obtained by reactions involved in the anaerobic metabolism of amino acids, simulated by providing 2-oxoglutarate and malate to mitochondria. Energy production was limited by rates of oxidant equivalent generation under the latter condition. Our data suggest that acetoacetate could effectively contribute to sustaining anaerobic energy production from endogenous substrates in liver tissue.
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Affiliation(s)
- R Guidoux
- Nestec Ltd, Research Centre, Vers-chez-les-Blanc, Lausanne, Switzerland
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14
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MacDonald MJ, Fahien LA, Mertz RJ, Rana RS. Effect of esters of succinic acid and other citric acid cycle intermediates on insulin release and inositol phosphate formation by pancreatic islets. Arch Biochem Biophys 1989; 269:400-6. [PMID: 2645827 DOI: 10.1016/0003-9861(89)90123-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Esters of carboxylic acids are permeable to cells and once inside the cell are hydrolyzed to carboxylic acids. Methyl and ethyl esters of succinate and other citric acid cycle intermediates were tested to find out whether they are insulin secretagogues. Monomethyl succinate stimulated insulin release from pancreatic islets in a concentration-dependent manner with maximal release attained at a concentration of 10 mM. Dimethyl succinate (10 mM) was as effective as monomethyl succinate, but pyruvate methyl ester, monoethyl succinate, and dimethyl fumarate were ineffective as primary secretagogues. However, dimethyl fumarate potentiated both leucine- and leucine-plus-glutamine-induced insulin release. Glucose, leucine, leucine plus glutamine, and monomethyl succinate increased inositol tris-, bis- and monophosphate formation in pancreatic islets and antimycin A inhibited this formation. Since mitochondrial metabolism is probably essential for glucose-induced insulin release and the metabolism of succinate and leucine (without or with glutamine) involves mitochondrial respiration exclusively, these results might indicate that mitochondrial metabolism generates conditions or factors that are transmitted to the cytosol to increase inositol trisphosphate formation and thus calcium mobilization and insulin release. Since succinate is believed to enter metabolism at site II of the mitochondrial respiratory chain, it is interesting that rotenone, an inhibitor of NADH dehydrogenase and site I of the respiratory chain, was a potent inhibitor of monomethyl succinate-induced insulin released. Rotenone also inhibited leucine (plus or minus glutamine)-induced insulin release. These results indicate that beta cell metabolism of monomethyl succinate and leucine, like glucose, influences dehydrogenases that produce NADH.
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Affiliation(s)
- M J MacDonald
- Department of Pediatrics, University of Wisconsin Medical School, Madison, 53706
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15
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Jenkins TM, Weitzman PD. Physiological roles of animal succinate thiokinases. Specific association of the guanine nucleotide-linked enzyme with haem biosynthesis. FEBS Lett 1988; 230:6-8. [PMID: 3350152 DOI: 10.1016/0014-5793(88)80629-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The discovery of two distinct succinate thiokinases in mammalian tissues, one (G-STK) specific for GDP/GTP and the other (A-STK) for ADP/ATP, poses the question of their differential metabolic roles. Evidence has suggested that the A-STK functions in the citric acid cycle in the direction of succinyl-CoA breakdown (and ATP formation) whereas one role of the G-STK appears to be the re-cycling of succinate to succinyl-CoA (at the expense of GTP) for the purpose of ketone body activation. A third metabolic participation of succinyl-CoA is in haem biosynthesis. This communication shows that in chemically induced hepatic porphyria, when the demand for succinyl-CoA is increased, it is the level of G-STK only which is elevated, that of A-STK being unaffected. The results implicate G-STK in the provision of succinyl-CoA for haem biosynthesis, a conclusion which is further supported by the observation of a high G-STK/A-STK ratio in bone marrow.
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Affiliation(s)
- T M Jenkins
- Department of Biochemistry, University of Bath, England
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16
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Henning WD, Upton C, McFadden G, Majumdar R, Bridger WA. Cloning and sequencing of the cytoplasmic precursor to the alpha subunit of rat liver mitochondrial succinyl-CoA synthetase. Proc Natl Acad Sci U S A 1988; 85:1432-6. [PMID: 3422742 PMCID: PMC279785 DOI: 10.1073/pnas.85.5.1432] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Succinyl-CoA synthetase [succinate-CoA ligase (GDP-forming); EC 6.2.1.4] of rat liver, an alpha beta dimer, is a component of the enzymology of the tricarboxylic acid cycle and functions within the mitochondrial matrix. We have isolated and determined the sequence of a cDNA clone containing the coding sequence of the cytoplasmic precursor to the alpha subunit of this enzyme together with stretches of nontranslated sequence at the 5' and 3' ends. The translated amino acid sequence indicates the presence of a 27-residue N-terminal signal sequence for mitochondrial targeting. The amino acid sequence of the mature alpha subunit shows an extraordinary degree of homology to the alpha subunit of Escherichia coli succinyl-CoA synthetase, with greater than 70% of the residues identical. This suggests that the fundamental differences in the quaternary structures and catalytic functions of the mammalian and bacterial enzymes must be attributable to differences in the beta subunits. mRNA that hybridizes to the cloned DNA is approximately equal to 1800 nucleotide residues in length, confirming that each of the two subunits is encoded separately and does not arise by proteolysis of a primary gene product containing both subunits of the mature protein.
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Affiliation(s)
- W D Henning
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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17
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Jenkins TM, Eisenthal R, Weitzman PD. Two distinct succinate thiokinases in both bloodstream and procyclic forms of Trypanosoma brucei. Biochem Biophys Res Commun 1988; 151:257-61. [PMID: 3348777 DOI: 10.1016/0006-291x(88)90587-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Two succinate thiokinase activities specific for either adenine or guanine nucleotides have been found in Trypanosoma brucei. Key glycolytic and citric acid cycle enzymes were measured to show repression of glycolysis and derepression of the citric acid cycle in the procyclic form, relative to the bloodstream form. A marked rise in adenine-linked succinate thiokinase activity accompanied a rise in activity of citric acid cycle enzymes. However, guanine-linked succinate thiokinase was found to increase only slightly in activity. These results implicate the adenine-linked enzyme as an essential component of the citric acid cycle, whereas the guanine-linked enzyme appears to be under separate control. This communication also reports for the first time the occurrence of citrate synthase activity in the bloodstream (long slender) form of T. brucei.
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Affiliation(s)
- T M Jenkins
- Department of Biochemistry, University of Bath, U.K
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18
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Jenkins TM, Weitzman PD. Distinct physiological roles of animal succinate thiokinases. Association of guanine nucleotide-linked succinate thiokinase with ketone body utilization. FEBS Lett 1986; 205:215-8. [PMID: 2943604 DOI: 10.1016/0014-5793(86)80900-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Two distinct succinate thiokinases have recently been shown to exist in animal tissues, one specific for guanine nucleotide and the other for adenine nucleotide. Their physiological roles have here been investigated by comparing the levels of the two enzymes in liver and brain of normal and diabetic rats. A marked rise in the level of brain guanine nucleotide-linked succinate thiokinase in the diabetic condition is consistent with an enhanced utilization of ketone bodies and hence with the associated elevated demand for succinyl-CoA for the activation of acetoacetate. Taken together with the reported mitochondrial values of the ATP/ADP and GTP/GDP ratios, the results are interpreted to indicate that the adenine nucleotide-linked enzyme functions as a component of the citric acid cycle whereas the guanine nucleotide-linked enzyme functions in the opposite metabolic direction to produce succinyl-CoA from succinate.
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