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1.
Johan D.M. Olsson 《Carbohydrate research》2010,345(10):1331-1338
2-(N-Benzyloxycarbonyl)aminoethyl 7-O-acetyl-6-O-allyl-2-O-benzoyl-4-O-benzyl-3-O-chloroacetyl-l-glycero-α-d-manno-heptopyranosyl-(1→3)-[2,3,4,6-tetra-O-benzoyl-β-d-glucopyranosyl-(1→4)]-6,7-di-O-acetyl-2-O-benzyl-l-glycero-α-d-manno-heptopyranoside, a spacer-equipped protected derivative of the common 3,4-branched diheptoside trisaccharide structure of the lipopolysaccharide core of Neisseria meningitidis and Haemophilus influenzae has been synthesized. The protecting group pattern installed allows regioselective introduction of phosphoethanolamine residues in the 3- and 6-position of the second heptose unit in accordance with native structures. From this intermediate the 3-and 6-monophosphoethanolamine as well as the non-phosphorylated deprotected trisaccharides have been synthesized to be used in evaluation of antibody binding specificity and in investigation of the substrate specificity of glycosyl transferases involved in the biosynthesis of LPS core structures. 相似文献
2.
N-Methylaspartate-Evoked Liberation of Taurine and Phosphoethanolamine In Vivo: Site of Release 总被引:2,自引:1,他引:1
The effect of N-methyl-D,L-aspartic acid (NMA) on extracellular amino acids was studied in the rabbit hippocampus with the brain dialysis technique. Administration of 0.5 or 5 mM NMA caused a concentration-dependent liberation of taurine and phosphoethanolamine (PEA). Taurine increased by 1,200% and PEA by 2,400% during perfusion with 5 mM NMA whereas most other amino acids rose by 20-100%. The effect of NMA appeared to be receptor-mediated, as coperfusion with D-2-amino-5-phosphonovaleric acid curtailed the NMA response by some 90%. The NMA-stimulated release of taurine and PEA was suppressed when Ca2+ was omitted and further inhibited when Co2+ was included in the perfusion medium. The effect of NMA was mimicked by the endogenous NMA agonist quinolinic acid and the partial NMA agonist D,L-cis-2,3-piperidine dicarboxylic acid. Although the NMA-evoked release of taurine and PEA was Ca2+-dependent in vivo, NMA had no effect on Ca2+ accumulation in hippocampal synaptosomes. The previously reported NMA-induced activation of dendritic Ca2+ spikes and the lack of effect on synaptosomal Ca2+ uptake suggest that taurine and PEA are released from sites other than nerve terminals, possibly from dendrosomatic sites. This notion was strengthened by the absence of an effect of NMA on the efflux of radiolabelled taurine from hippocampal synaptosomes. In contrast, high K+ stimulated synaptosomal uptake of Ca2+ and release of taurine. 相似文献
3.
Phospholipid Biosynthesis in Myelin: Presence of CTP: Phosphoethanolamine Cytidylyltransferase in Purified Myelin of Rat Brain 总被引:4,自引:4,他引:0
Highly purified myelin from rat brain was previously shown to contain the ethanolaminephosphotransferase which completes the synthesis of phosphatidyl ethanolamine. We have now obtained evidence for the presence in myelin of CTP:phosphoethanolamine cytidylyltransferase, the enzyme catalyzing formation of CDP-ethanolamine. Myelin was isolated by two different procedures, one based on the Norton-Poduslo method and the other involving repetitive gradients with osmotic shocking deferred to the end. The fact that activity remained constant through all but the earliest steps suggested that the enzyme is intrinsic to myelin. Comparison of subcellular fractions revealed that approximately half the total activity was in the supernatant, the remainder being distributed among the particulate fractions. Relative specific activity of myelin was 27-31% that of microsomes, thus eliminating the possibility of appreciable contamination by the latter. The possibility of adsorption of the soluble enzyme by myelin was rendered unlikely by retention of activity after washing the myelin with buffered sodium chloride or sodium taurocholate. Furthermore, relative specific activity of the cytidylyltransferase was 10-fold higher than that of lactate dehydrogenase (a cytosolic marker) in myelin. The apparent Km for CTP was approximately the same for myelin and microsomes, but that for phosphoethanolamine was significantly higher for myelin. 相似文献
4.
In Vivo Substitution of Choline for Sodium Evokes a Selective Osmoinsensitive Increase of Extracellular Taurine in the Rat Hippocampus 总被引:1,自引:0,他引:1
Recent investigations have demonstrated that taurine and phosphoethanolamine (PEA) are the amino acids most sensitive to microdialysis-perfusion with reduced concentrations of NaCl. The aim of the present work was to assess the importance of Na+ deficiency in evoking this response. Further, the previously described selectivity of replacement of Cl- with acetate with respect to amino acid release was reinvestigated. The hippocampus of urethane-anesthetized rats was dialyzed with Krebs-Ringer bicarbonate buffer, and amino acid concentrations of the perfusate were determined. Choline chloride was then stepwise substituted for NaCl, and, in some cases, mannitol (122 mM) was included in low sodium-containing media. In other experiments, NaCl was replaced with sodium acetate. The dialysate levels of taurine increased selectively in response to Na+ substitution. The elevation of taurine was linearly related to the increase in choline chloride, and maximal levels amounted to 335% of basal levels. The increase in extracellular taurine was not inhibited by perfusion with medium made hyperosmotic with mannitol. Replacement of Cl- with acetate stimulated the release of taurine to 652% of resting levels. In addition, PEA levels increased to 250% of control concentration. Other amino acids were unaffected by Cl- substitution. The results show that taurine transport is considerably more sensitive to Na+ depletion than glutamate transport, which also is known to be Na+ dependent. The taurine increase evoked by low Na+ is not caused by cellular swelling as it was unaffected by hyperosmolar medium. Finally, substitution of acetate for Cl- causes a specific elevation of extracellular taurine and PEA, possibly as a result of cytotoxic edema. 相似文献
5.
The conversion of phosphoethanolamine to phosphocholine requires 3 separate N-methyltransferases. We had previously purified the enzyme catalyzing the last methylation, phosphodimethylethanolamine N-methyltransferase. We have successfully purified the enzyme catalyzing the initial methylation of phosphoethanolamine. A 434 fold purified enzyme from rat brain was obtained by the sequential use of ammonium sulfate fractionation, Q-Sepharose fast flow column chromatography and a -aminoethyl agarose column chromatography. The pH optimum was 11 or greater, the Km value for phosphoethanolamine was 167.8±41.7 M and the Vmax was 487.3±85 mmoles/mg/hr. The kinetics for S-adenosyl-methionine, the methyldonor, has characteristics of cooperative binding with a Km of 1.805±0.59 mM and a Vmax of 16.9±3.6 moles/mg/hr. The activity was stimulated 6 fold by 2.5 mM MnCl2 and inhibited by DZA and S-adenosylhomocysteine. These results reinforce the early in vivo observations which had provided suggestive evidence for the existence of a pathway for the methylation of phosphoethanolamine to phosphocholine in rat brain.Abbreviations used Adomet
S-adenosylmethionine
- AdoHcy
S-adenosyl-homocysteine
- CAPS
3-(cyclohexyl)amino-1-propanesulphonic acid
- Cho
choline
- 3-DZA
3-deazaadenosine
- Etn
ethanolamine
- N-MT
N-methyltransferase
- PEG
polyethyleneglycol
- PMSF
phenylmethanesulphonyl fluoride
- PEtn
phosphoethanolamine
- PCho
phosphocholine
- PMe2Etn
phosphodimethylethanolamine
- PtdCho
phosphatidylcholine
- PtdEtn
phosphatidylethanolamine 相似文献
6.
Vishal M. Gohil Lin Zhu Charli D. Baker Valentin Cracan Abbas Yaseen Mohit Jain Clary B. Clish Paul S. Brookes Marica Bakovic Vamsi K. Mootha 《The Journal of biological chemistry》2013,288(49):35387-35395
We recently identified meclizine, an over-the-counter drug, as an inhibitor of mitochondrial respiration. Curiously, meclizine blunted respiration in intact cells but not in isolated mitochondria, suggesting an unorthodox mechanism. Using a metabolic profiling approach, we now show that treatment with meclizine leads to a sharp elevation of cellular phosphoethanolamine, an intermediate in the ethanolamine branch of the Kennedy pathway of phosphatidylethanolamine biosynthesis. Metabolic labeling and in vitro enzyme assays confirmed direct inhibition of the cytosolic enzyme CTP:phosphoethanolamine cytidylyltransferase (PCYT2). Inhibition of PCYT2 by meclizine led to rapid accumulation of its substrate, phosphoethanolamine, which is itself an inhibitor of mitochondrial respiration. Our work identifies the first pharmacologic inhibitor of the Kennedy pathway, demonstrates that its biosynthetic intermediate is an endogenous inhibitor of respiration, and provides key mechanistic insights that may facilitate repurposing meclizine for disorders of energy metabolism. 相似文献
7.
Wu S Yu Z Wang F Li W Ye C Li J Tang J Ding J Zhao J Wang B 《Molecular biotechnology》2007,36(2):102-112
N-methylation of phosphoethanolamine, the committing step in choline (Cho) biosynthesis in plants, is catalyzed by S-adenosyl-l-methionine: phosphoethanolamine N-methyltransferase (PEAMT, EC 2.1.1.103). Herein we report the cloning and characterization of the novel maize phosphoethanolamine
N-methyltransferase gene (ZmPEAMT1) using a combination of bioinformatics and a PCR-based allele mining strategy. The cDNA sequence of ZmPEAMT1 gene is 1,806 bp in length and translates a 495 amino acids peptide. The upstream promoter sequence of ZmPEAMT1 were obtained by TAIL-PCR, and contained four kinds of putative cis-acting regulatory elements, including stress-responsive elements, phytohormone-responsive elements, pollen developmental
special activation elements, and light-induced signal transduction elements, as well as several other structural features
in common with the promoter of rice and Arabidopsis homologies. RT-PCR analysis showed that expression of ZmPEAMT1 was induced by salt stress and suppressed by high temperature. Over-expression of ZmPEAMT1 enhanced the salt tolerance, root length, and silique number in transgenic Arabidopsis. These data indicated that ZmPEAMT1 maybe involved in maize root development and stress resistance, and maybe having a potential application in maize genetic
engineering.
Note: Nucleotide sequence data are available in GenBank under the following accession numbers: maize (Zea mays, ZmPEAMT1, AY626156; ZmPEAMT2, AY103779); rice (Oryza sativa, OsPEAMT1/Os01g50030, NM_192178; OsPEAMT2/Os05g47540, XM_475841); wheat (Triticum aestivum, TaPEAMT, AY065971); Arabidopsis (Arabidopsis thaliana, AtNMT1/At3g18000, AY091683; AtNMT2/At1g48600, NM_202264; AtNMT3/At1g73600, NM_106018); oilseed rape (Brassica napus, BnPEAMT, AY319479), tomato (Lycopersicon esculentum, AF328858), spinach (Spinacia oleracea, AF237633). 相似文献
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10.
Summary. This study investigates the relationship between changes in plasma sodium and changes in amino acid levels in a patient with
post-traumatic sepsis and prolonged critical illness. Ninety-two consecutive measurements were performed at regular intervals
over a period of many weeks; these consisted in the determination of full amino-acidograms, plasma sodium and complementary
variables. A unique, highly significant inverse correlation between taurine and plasma sodium was found (r2 = 0.48, p < 0.001). All other amino acids were unrelated, or much more weakly related, to sodium. Taurine was also strongly
and directly related to phosphoethanolamine, glutamate and aspartate. Changes in sodium and in levels of these amino acids
explained up to 86% of the variability of taurine. Besides, levels of these amino acids maintained a high degree of co-variation,
remaining reciprocally related one to each other, directly, with r2 ranging between 0.33 and 0.59 (p < 0.001 for all). There were similar findings for β-alanine, which however was measured inconsistently. These data provide gross clinical evidence of a specific link binding
plasma sodium and taurine levels, and may be consistent with occurrence of opposite and interdependent shifts of sodium and
taurine between intravascular and extravascular space, to maintain osmoregulation. Co-variation of taurine with the other
amino acids may be related to the same phenomenon, and/or to similarities in transport systems and chemical structure, or
true metabolic interactions.
Received April 16, 2002 Accepted June 19, 2002 Published online November 14, 2002
RID="*"
ID="*" Presented at the 7th International Congress on Amino Acids and Proteins, Vienna (Austria), August 6–10, 2001.
Acknowledgements The authors acknowledge the kind assistance of Mr. Maurizio Cianfanelli, from the Catholic University School of Medicine,
Rome, Italy.
Authors' address: Dr. Carlo Chiarla, Via Augusto Tebaldi, 19, I-00168 Roma, Italy, E-mail: carlo.chiarla@rm.unicatt.it 相似文献