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Mishanina TV, Yu L, Karunaratne K, Mondal D, Corcoran JM, Choi MA, Kohen A. An unprecedented mechanism of nucleotide methylation in organisms containing thyX. Science 2016; 351:507-10. [PMID: 26823429 DOI: 10.1126/science.aad0300] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
In several human pathogens, thyX-encoded flavin-dependent thymidylate synthase (FDTS) catalyzes the last step in the biosynthesis of thymidylate, one of the four DNA nucleotides. ThyX is absent in humans, rendering FDTS an attractive antibiotic target; however, the lack of mechanistic understanding prohibits mechanism-based drug design. Here, we report trapping and characterization of two consecutive intermediates, which together with previous crystal structures indicate that the enzyme's reduced flavin relays a methylene from the folate carrier to the nucleotide acceptor. Furthermore, these results corroborate an unprecedented activation of the nucleotide that involves no covalent modification but only electrostatic polarization by the enzyme's active site. These findings indicate a mechanism that is very different from thymidylate biosynthesis in humans, underscoring the promise of FDTS as an antibiotic target.
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Affiliation(s)
| | - Liping Yu
- Nuclear Magnetic Resonance (NMR) Core Facility and Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | | | - Dibyendu Mondal
- Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA
| | - John M Corcoran
- Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA
| | - Michael A Choi
- Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA
| | - Amnon Kohen
- Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA
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2
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Al-Saeedi F, Welch AE, Smith TAD. [methyl-3H]Choline incorporation into MCF7 tumour cells: correlation with proliferation. Eur J Nucl Med Mol Imaging 2005; 32:660-7. [PMID: 15660258 DOI: 10.1007/s00259-004-1707-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2004] [Accepted: 09/15/2004] [Indexed: 10/25/2022]
Abstract
PURPOSE The aim of the study was to investigate the intracellular location of [methyl-(3)H]choline in MCF7 tumour cells and to determine the relationship between [methyl-(3)H]choline incorporation and proliferation. METHODS Tumour cells were incubated with [methyl-(3)H]choline for 10 min, and then in cold medium to simulate the rapid blood clearance of [methyl-(11)C]choline. Labelled metabolites were then extracted from cells by treating them with organic and aqueous solvents to determine the distribution of tracer between phospholipid and water-soluble metabolite pools. Aqueous extracts were subjected to thin-layer chromatography, ion exchange chromatography and a choline extraction procedure to identify (3)H-containing metabolites. Procedures were carried out on fast- and slow-growing populations of MCF7 cells to determine the relationship between choline incorporation and proliferation. RESULTS Only about 5% of [methyl-(3)H]choline was present as phospholipid. [methyl-(3)H]choline incorporation was found to be related to S-phase fraction. In another experiment, [methyl-(14)C]choline incorporation was found to be correlated with [methyl-(3)H]thymidine incorporation. The V(max) of choline uptake was found to be increased whilst K(m) was decreased in populations of MCF7 cells with higher proliferative fractions, compared with populations having lower proliferative fractions. CONCLUSION Choline incorporation into tumour cells under conditions that simulate rapid blood clearance of [methyl-(11)C]choline is correlated with proliferation. Most of the activity (about 95%) was in the non-lipid fraction of the cell.
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Affiliation(s)
- Fatma Al-Saeedi
- John Mallard PET Centre Department of Biomedical Physics and Bioengineering, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
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3
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Norén B, Lundberg P, Ressner M, Wirell S, Almer S, Smedby O. Absolute quantification of human liver metabolite concentrations by localized in vivo 31P NMR spectroscopy in diffuse liver disease. Eur Radiol 2004; 15:148-57. [PMID: 15351899 DOI: 10.1007/s00330-004-2434-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2003] [Revised: 06/04/2004] [Accepted: 06/28/2004] [Indexed: 12/13/2022]
Abstract
Phosphorus-31 NMR spectroscopy using slice selection (DRESS) was used to investigate the absolute concentrations of metabolites in the human liver. Absolute concentrations provide more specific biochemical information compared to spectrum integral ratios. Nine patients with histopathologically proven diffuse liver disease and 12 healthy individuals were examined in a 1.5-T MR scanner (GE Signa LX Echospeed plus). The metabolite concentration quantification procedures included: (1) determination of optimal depth for the in vivo measurements, (2) mapping the detection coil characteristics, (3) calculation of selected slice and liver volume ratios using simple segmentation procedures and (4) spectral analysis in the time domain. The patients had significantly lower concentrations of phosphodiesters (PDE), 6.3+/-3.9 mM, and ATP-beta, 3.6+/-1.1 mM, (P<0.05) compared with the control group (10.0+/-4.2 mM and 4.2+/-0.3 mM, respectively). The concentrations of phosphomonoesters (PME) were higher in the patient group, although this was not significant. Constructing an anabolic charge (AC) based on absolute concentrations, [PME]/([PME] + [PDE]), the patients had a significantly larger AC than the control subjects, 0.29 vs. 0.16 (P<0.005). Absolute concentration measurements of phosphorus metabolites in the liver are feasible using a slice selective sequence, and the technique demonstrates significant differences between patients and healthy subjects.
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Affiliation(s)
- Bengt Norén
- Depatment of Radiology/IMV, Linköping University, 581-85 Linköping, Sweden
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4
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Berrie CP, Dragani LK, van der Kaay J, Iurisci C, Brancaccio A, Rotilio D, Corda D. Maintenance of PtdIns45P2 pools under limiting inositol conditions, as assessed by liquid chromatography-tandem mass spectrometry and PtdIns45P2 mass evaluation in Ras-transformed cells. Eur J Cancer 2002; 38:2463-75. [PMID: 12460792 DOI: 10.1016/s0959-8049(02)00485-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Inositol-containing molecules are involved in important cellular functions, including signalling, membrane transport and secretion. Our interest is in lysophosphatidylinositol and the glycerophosphoinositols, which modulate cell proliferation and G-protein-dependent activities such as adenylyl cyclase and phospholipase A(2). To investigate the role of glycerophosphoinositol (GroPIns) in the modulation of Ras-dependent pathways and its correlation to Ras transformation, we employed a novel liquid chromatography-tandem mass spectrometry technique to directly measure GroPIns in cell extracts. The cellular levels of GroPIns in selected parental and Ras-transformed cells, and in some carcinoma cells, ranged from 44 to 925 microM, with no consistent correlation to Ras transformation across all cell lines. Moreover, the derived cellular inositol concentrations revealed a wide range ( approximately 150 microM to approximately 100 mM) under standard [(3)H]-inositol-loading, suggesting a complex relationship between the inositol pool and the phosphoinositides and their derivatives. We have investigated these pools under specific loading conditions, designing a further HPLC analysis for GroPIns, combined with mass determinations of cellular phosphatidylinositol 4,5-bisphosphate. The data demonstrate that limiting inositol conditions identify a preferred pathway of inositol incorporation and retention into the polyphosphoinositides pool. Thus, under conditions of increased metabolic activity, such as receptor stimulation or cellular transformation, the polyphosphoinositide levels will be maintained at the expense of phosphatidylinositol and the turnover of its aqueous derivatives.
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Affiliation(s)
- C P Berrie
- Department of Cell Biology and Oncology, Istituto di Ricerche Farmacologiche Mario Negri, Consorzio Mario Negri Sud, Via Nazionale, 66030 Santa Maria Imbaro (Chieti), Italy.
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5
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Mandal S, Richardson VJ, Banoub J, Church JG. Identification of myo-inositol 1,2-cyclic monophosphate by electrospray tandem mass spectrometry, a major constituent of EGF-stimulated phosphoinositide turnover in MDA 468 cells. Exp Cell Res 2002; 277:131-8. [PMID: 12083795 DOI: 10.1006/excr.2002.5549] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Epidermal growth factor (EGF) caused an increase in phosphoinositide (PI) turnover in MDA 468 cells. This EGF-stimulated effect was inhibited by the protein tyrosine kinase inhibitor lavendustin A (LA). MDA 468 cells generated an atypical PI turnover profile. Examination and quantitation of the PI metabolite profile showed that even control cells produced a metabolite which was acid-labile and which formed about 60% of the total PI metabolites. By using the technique of electrospray ionization tandem mass spectrometry, we were able to confirm the identity of this acid-labile metabolite through the specific fragmentation as compared with the standard. The precursor molecule fragmented into two distinct productions with molar masses identical to that of the standard myo-inositol 1,2-cyclic monophosphate (cInsP). Changes in the PI turnover profile could be accounted for by the alterations in myo-inositol 1,2-cyclic monophosphate generated in these cells. We thus conclude that, by some as-yet-unidentified mechanism, cyclic inositol monophosphate forms a major constituent of EGF-stimulated PI turnover in MDA 468 cells.
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Affiliation(s)
- Soma Mandal
- Terry Fox Cancer Research Laboratories, Memorial University of Newfoundland, St. John's, Canada A1B 3V6
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6
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Affiliation(s)
- L E Hokin
- Department of Pharmacology, University of Wisconsin Medical School, Madison 53706, USA
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Szwergold BS, Kappler F, Moldes M, Shaller C, Brown TR. Characterization of a phosphonium analog of choline as a probe in 31P NMR studies of phospholipid metabolism. NMR IN BIOMEDICINE 1994; 7:121-127. [PMID: 8080713 DOI: 10.1002/nbm.1940070304] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Tumors and transformed cells have been shown by 31P NMR to contain elevated concentrations of two phosphomonoesters, phosphorylcholine and phosphorylethanolamine, involved in phospholipid metabolism. In order to understand the biochemical basis for these phenomena new methods are needed to allow for analysis of the relevant metabolic pathways in intact cells. One such promising tool may be phosphonium-choline, a 31P NMR-visible analog of choline in which the trimethyl-ammonium group of choline has been replaced with a trimethyl-phosphonium moiety. As shown previously [Sim et al. Biochem. J. 154, 303 (1976)], this compound is non-toxic and readily metabolized by cultured cells into phospholipids. In this paper we describe in greater detail some of the chemical and NMR spectroscopic properties of this material. Most significantly we show here that the chemical shift of phosphonium-choline is sensitive to the phosphorylation state of the analog and that the phosphonium nucleus is NMR-visible even after its incorporation into phospholipid. The unique properties of this analog should make it possible to use high-field 31P NMR to follow the flux of phosphonium-choline through the Kennedy pathway in intact perfused cells cultures.
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8
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Burt CT, Moore RR, Roberts MF. In vivo 19F NMR studies of hyperthermia: hydrophobic environments probed by halothane. NMR IN BIOMEDICINE 1993; 6:289-296. [PMID: 8268060 DOI: 10.1002/nbm.1940060502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The steady-state distribution of the general anesthetic halothane in different rat tissues, including a renal adenocarcinoma with and without hyperthermia treatment, has been evaluated by in vivo 19F NMR spectroscopy. The 19F spectra of halothane (which is a hydrophobic probe) from within tissue show differences in the partitioning between normal rat tissues and adenocarcinoma. Muscle, as a control tissue, exhibits a single large resonance around 0 ppm. However, the adenocarcinoma exhibits two slow-exchanging resonances separated by 0.3 ppm with the one at the more hydrophobic chemical shift being more sensitive to hyperthermia treatment. The results from this tumor model suggest that 19F NMR spectroscopy may be useful first in detecting a change in hydrophobic environments using a lipophilic probe such as halothane, and secondly in monitoring the effects of hyperthermia, a treatment whose effectiveness may involve changes at the level of the plasma membrane. Under conditions of continuous delivery, a resonance which is not detected in the spectra of halothane in excised tissue appears 5 ppm downfield from the resonance for halothane localized in tissues. A rotating frame experiment is used to show that this resonance is derived from anesthetic absorbed on the tissue surface.
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Affiliation(s)
- C T Burt
- MRI Center, University of Illinois at Chicago 60680
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9
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Smith TA, Bush C, Jameson C, Titley JC, Leach MO, Wilman DE, McCready VR. Phospholipid metabolites, prognosis and proliferation in human breast carcinoma. NMR IN BIOMEDICINE 1993; 6:318-323. [PMID: 8268064 DOI: 10.1002/nbm.1940060506] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The content of the phospholipid metabolites, phosphocholine, phosphoethanolamine, glycerophosphorylcholine and glycerophosphorylethanolamine was measured in chemical extracts from 46 human breast carcinoma using 31P NMR spectroscopy. Some patients had received therapy prior to tumour resection. The data were therefore stratified into two groups: (i) all tumours; and (ii) untreated tumours. Three indices of tumour proliferation i.e., mitotic index, Ki67 and S-phase fraction were determined on tissue from the same tumours and were found not to correlate with the content of any of these metabolites. In addition oestrogen-receptor status and density, tumour grade and DNA ploidy were obtained on some tumours. The phosphocholine content was higher in high grade tumours when compared with low grade tumours. There was no apparent relationship between DNA ploidy and the content of any of these metabolites. Glycerophosphorylcholine content of oestrogen-receptor positive tumours correlated with receptor density. However, there was no significant difference between receptor positive and negative tumours in the content of any of the phospholipid metabolites measured.
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MESH Headings
- Aneuploidy
- Breast Neoplasms/chemistry
- Breast Neoplasms/mortality
- Breast Neoplasms/pathology
- Breast Neoplasms/therapy
- Carcinoma, Ductal, Breast/chemistry
- Carcinoma, Ductal, Breast/mortality
- Carcinoma, Ductal, Breast/pathology
- Carcinoma, Ductal, Breast/therapy
- DNA, Neoplasm/analysis
- Ethanolamines/analysis
- Female
- Glycerylphosphorylcholine/analysis
- Humans
- Ki-67 Antigen
- Magnetic Resonance Spectroscopy
- Mitotic Index
- Neoplasm Proteins/analysis
- Nuclear Proteins/analysis
- Phosphatidylethanolamines/analysis
- Phospholipids/analysis
- Phosphorylcholine/analysis
- Prognosis
- Receptors, Estrogen/analysis
- S Phase
- Tissue Extracts
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Affiliation(s)
- T A Smith
- Department of Nuclear Medicine, Royal Marsden Hospital, Sutton, Surrey, UK
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10
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Smith TA, Baluch S, Titley JC, Ormerod MG, Eccles S, Tombs AJ, Leach MO, Griffiths JR, McCready VR. The effect of oestrogen ablation on the phospholipid metabolite content of primary and transplanted rat mammary tumours. NMR IN BIOMEDICINE 1993; 6:209-214. [PMID: 8347455 DOI: 10.1002/nbm.1940060307] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The concentration of phospholipid metabolites was determined in chemical extracts from two types of rat mammary tumours and compared with proliferation data (S-phase fraction). One of the tumours was an oestrogen-sensitive transplanted tumour. In this tumour the concentration of phosphocholine (PC) and glycerophosphorylcholine (GPC) correlated strongly with the S-phase fraction but not with the number of cells actively synthesizing DNA. Oestrogen ablation resulted in tumour regression. Regressing tumours contained less PC and more GPC than those actively growing. The other tumour was induced in rats by intravenous administration of N-methyl N-nitrosourea. Phosphoethanolamine (PE), PC and GPC levels were not associated with the S-phase fraction in this tumour. Oestrogen ablation resulted in tumour regression. There was no significant difference between the regressing and growing tumours in PE, PC or GPC content.
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Affiliation(s)
- T A Smith
- Department of Nuclear Medicine, Royal Marsden Hospital and Institute of Cancer Research, Sutton, Surrey, UK
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11
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Ruiz-Cabello J, Cohen JS. NMR and the study of pathological state in cells and tissues. INTERNATIONAL REVIEW OF CYTOLOGY 1993; 145:1-63. [PMID: 8500979 DOI: 10.1016/s0074-7696(08)60424-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- J Ruiz-Cabello
- Department of Pharmacology, Georgetown University Medical School, Washington, D.C. 20007
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12
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Navon G, Kushnir T, Askenasy N, Kaplan O. Two-Dimensional 31P-1H Correlation Spectroscopy in Intact Organs and Their Extracts. IN-VIVO MAGNETIC RESONANCE SPECTROSCOPY II: LOCALIZATION AND SPECTRAL EDITING 1992. [DOI: 10.1007/978-3-642-77208-5_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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13
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Kaplan O, van Cohen PCM, Cohen JS. NMR Studies of Metabolism of Cells and Perfused Organs. IN-VIVO MAGNETIC RESONANCE SPECTROSCOPY III: IN-VIVO MR SPECTROSCOPY: POTENTIAL AND LIMITATIONS 1992. [DOI: 10.1007/978-3-642-77218-4_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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14
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Ross TS, Majerus PW. Inositol-1,2-cyclic-phosphate 2-inositolphosphohydrolase. Substrate specificity and regulation of activity by phospholipids, metal ion chelators, and inositol 2-phosphate. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(17)35251-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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15
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Shears SB. Regulation of the metabolism of 1,2-diacylglycerols and inositol phosphates that respond to receptor activation. Pharmacol Ther 1991; 49:79-104. [PMID: 1649478 DOI: 10.1016/0163-7258(91)90023-f] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This review assimilates information on the regulation of the metabolism of those inositol phosphates and diacylglycerols that respond to receptor activation. Particular emphasis is placed on the regulation of specific enzymes, the occurrence of isoenzymes, and metabolic compartmentalization; the overall aim is to demonstrate the significance of these activities in relation to the physiological impact of the various cell signalling processes.
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Affiliation(s)
- S B Shears
- Inositol Lipid Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709
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16
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Szwergold BS, Kappler F, Cohen LH, Nanavati D, Brown TR. Identification of a naturally occurring methyl-ester of phosphate, methyl-phosphorylcholine (methyl-2-(N,N,N trimethylamino) ethyl phosphate), in the eggs of the sea urchin S. purpuratus. Biochem Biophys Res Commun 1990; 172:855-61. [PMID: 2241973 DOI: 10.1016/0006-291x(90)90754-b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A novel metabolite of choline, phosphorylcholine methyl ester, has been identified in the eggs of S. purpuratus wherein it is present at approximately 1 mM concentration. To the best of our knowledge, this is the first instance of a phosphoryl-methyl-ester to be observed in nature. The compound appears to be species specific, since it has not been observed in other species such as L. pictus and P. depressus. In S. purpuratus its distribution is confined to the ovary, eggs and embryos, and is absent from young animals following metamorphosis.
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Affiliation(s)
- B S Szwergold
- Dept. of NMR and Medical Spectroscopy, Fox Chase Cancer Center, Philadelphia, Pa. 19111
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17
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Ross TS, Tait JF, Majerus PW. Identity of inositol 1,2-cyclic phosphate 2-phosphohydrolase with lipocortin III. Science 1990; 248:605-7. [PMID: 2159184 DOI: 10.1126/science.2159184] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The amino acid sequences of three fragments of cyanogen bromide-digested human placental inositol 1,2-cyclic phosphate 2-phosphohydrolase, an enzyme of the phosphatidylinositol signaling pathway, are identical to sequences within lipocortin III, a member of a family of homologous calcium- and phospholipid-binding proteins that do not have defined physiological functions. Lipocortin III has also been previously identified as placental anticoagulant protein III (PAP III) and calcimedin 35 alpha. Antibodies to PAP III detected PAP III and inositol 1,2-cyclic phosphate 2-phosphohydrolase with identical reactivity on immunoblotting. In addition, inositol 1,2-cyclic phosphate 2-phosphohydrolase was stimulated by the same acidic phospholipids that bind lipocortins.
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Affiliation(s)
- T S Ross
- Department of Internal Medicine, Washington University School of Medicine, St Louis, MO 63110
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18
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Rayner MH, Sadler PJ, Scawen MD. NMR studies of a bacterial cell culture medium (LB broth): cyclic nucleotides in yeast extracts. FEMS Microbiol Lett 1990; 56:217-21. [PMID: 2185126 DOI: 10.1111/j.1574-6968.1990.tb04152.x] [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: 12/30/2022] Open
Abstract
The composition of LB broth (tryptone, yeast extract and NaCl) was investigated by 1H,31P-NMR spectroscopy, FPLC and gel electrophoresis. An unexpected finding was the high level of 2'3'-cyclic nucleotides, detected by characteristic 31P-NMR resonances in the region 20-21 ppm, originating from the yeast component. 31P-NMR resonances for cyclic nucleotides were observed during the autolysis of Saccharomyces cerevisiae cells, and in model reactions of RNase with RNA.
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Affiliation(s)
- M H Rayner
- Department of Chemistry, Birkbeck College, Gordon House, Laboratory, London, U.K
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19
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Abstract
Interest in the inositol phospholipids was stimulated by the simultaneous discoveries that the products of hydrolysis of these lipids could serve as messengers to activate to synergistic signaling pathways in hormonally responsive cells, namely, inositol 1,4,5-trisphosphate which causes the release of Ca2+ from intracellular stores and diacylglycerol which promotes the activation of protein kinase C. At the same time, Berridge and co-workers introduced relatively simple approaches to study the inositol phospholipid cycle. These included the use of [3H]inositol to label the inositol metabolites, all of which are confined to this cycle, and of Li+ to decrease the rate of degradation of the inositol phosphates. Water-soluble inositol phosphates and chloroform-soluble inositol phospholipids could then be separated by solvent partition and the inositol phosphates further separated by use of an anion-exchange resin. However, the subsequent application of high-performance liquid chromatography as a separation technique indicated the existence of many isomers of the inositol phosphates formed by different pathways of dephosphorylation and phosphorylation. Mapping of these metabolic pathways may be substantially complete, but novel pathways may still be discovered. We review both old and new methods of analysis of the inositol phosphates for the measurement of mass and radioactivity. Although the complexity of the cycle sometimes demands the use of sophisticated methods of separation and rigorous identification, older and inexpensive methods may still be useful for some purposes.
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Affiliation(s)
- N M Dean
- Cancer Research Center of Hawaii, University of Hawaii, Honolulu 96813
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20
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Abstract
The 31P NMR spectrum of perfused rat liver was found to be dependent on the exogenous carbon available to the tissue. When pyruvate was supplied to liver initially perfused with lactate, Pi decreased, phosphoenol pyruvate and phosphomonoesters increased, and nucleotide pools remained the same. It is proposed that these changes can be used to evaluate liver function.
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Affiliation(s)
- W J Thoma
- Department of Biochemistry, University of Minnesota, Navarre 55392
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21
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Smith RE, MacQuarrie RA. Determination of inositol phosphates and other biologically important anions by ion chromatography. Anal Biochem 1988; 170:308-15. [PMID: 3394931 DOI: 10.1016/0003-2697(88)90636-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ion chromatography has been applied to the simultaneous, multi-component determination of biologically important anions. More than 20 different biologically important anions were separated on high performance ion-exchange columns and detected using chemically suppressed conductivity. Application of the technique to the separation of inositol mono-, bis-, and trisphosphates shows that these compounds can be separated from the other ions tested and can be detected at concentrations that may be found in vivo. For inositol monophosphate, the conductivity was proportional to the amount of compound from less than 20 pmol to more than 400 nmol. Although alternative methods are available for assaying each of these anions individually, the advantages of ion chromatography lie in the sensitivity of detection, the speed of separation, and the ability to simultaneously determine numerous ions. This method should be broadly applicable to studies of second messengers, measurements of reaction rates, and various metabolic studies.
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Affiliation(s)
- R E Smith
- School of Basic Life Sciences, University of Missouri, Kansas City 64110
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22
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23
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Williamson JR, Hansen CA, Johanson RA, Coll KE, Williamson M. Formation and metabolism of inositol phosphates: the inositol tris/tetrakisphosphate pathway. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1988; 232:183-95. [PMID: 3063078 DOI: 10.1007/978-1-4757-0007-7_20] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- J R Williamson
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104
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24
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Szwergold BS, Graham RA, Brown TR. Observation of inositol pentakis- and hexakis-phosphates in mammalian tissues by 31P NMR. Biochem Biophys Res Commun 1987; 149:874-81. [PMID: 3426614 DOI: 10.1016/0006-291x(87)90489-x] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In analyzing the 31P NMR spectra of extracts of mammalian tissues and cells we have identified inositol pentakis- and hexakis-phosphates in essentially all of the samples examined. These compounds were present at concentrations of at least 5-15 microM. While the sources and functions of these compounds in mammalian cells are not clear, they may play an important role in phosphoinositol metabolism. For example, one obvious possibility is that these compounds may be sources of or sinks for the Ca++ mobilizing inositol tris- and tetrakis-phosphates.
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Affiliation(s)
- B S Szwergold
- Nuclear Magnetic Resonance Laboratory, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111
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Brown TR, Graham RA, Szwergold BS, Thoma WJ, Meyer RA. Phosphorylated metabolites in tumors, tissues, and cell lines. Ann N Y Acad Sci 1987; 508:229-40. [PMID: 3439703 DOI: 10.1111/j.1749-6632.1987.tb32907.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- T R Brown
- NMR Department, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111
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