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Subcellular localization and ionic properties of acetyl-coenzyme A synthetase in the electric organ of Torpedo marmorata.

ABSTRACT: Acetyl-CoA synthetase activity was shown to be present in pure cholinergic synaptosomes from electric organ of Torpedo marmorata. After osmotic disruption of synaptosomes a substantial part of the activity was recovered in the soluble fraction. The effects of varying pH and increasing K+ concentrations on the synaptosomal enzyme activity were shown to differ from those observed with the mitochondrial enzyme. Whereas this latter enzyme showed optimal activity above pH 8.5, and a maximal activation in the presence of 120 mM-K+, the synaptosomal enzyme exhibited an optimal activity at pH 7.9 and a moderate K+ stimulatory effect with an optimal concentration of 30 mM.

SUBMITTER: Morot-Gaudry Y

PROVIDER: S-EPMC1161053 | biostudies-other | 1979 May

REPOSITORIES: biostudies-other

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Biosynthesis of acetyl-coenzyme A in the electric organ of Torpedo marmorata in relation to acetylcholine metabolism.

Project description:Formation of acetyl-CoA through acetyl-CoA synthetase (forward reaction) and through choline acyltransferase (backward reaction) was investigated in tissue extract from the electric organ of Torpedo marmorata. When the tissue extract was submitted to gel filtration on Sephadex G-25, the formation of acetyl-CoA by acetyl-CoA synthetase appeared fully dependent on ATP and CoA and partially dependent on acetate (an endogenous supply of acetate is discussed). Choline acetyltransferase was a potent source of acetyl-CoA, only requiring acetylcholine and CoA, and was much more efficient than acetyl-CoA synthetase for concentrations of acetylcholine likely to be present in nerve endings.

| S-EPMC1165028 | biostudies-other

Phospholipid turnover in Torpedo marmorata electric organ during discharge in vivo.

Project description:One electric organ of anaesthetized Torpedo marmorata was stimulated through electrodes placed on the electric lobe of the brain. Nerves to the other electric organ were cut to provide an unstimulated control. Glucose 6-[32P]phosphate was injected into each organ 16h before electrical stimulation. After stimulation for 10 min at 5 Hz, the organs were removed homogenized and centrifuged on a density gradient for the preparation of subcellular fractions. Stimulation increased the incorporation of 32P into phosphatidate, phosphatidylinositol and phosphatidylcholine. The increased phosphatidate labelling, but not that of the other two lipids, was seen in fractions rich in synaptic vesicles. Stimulation had no effect on ATP labelling. The phosphatidate content of most fractions fell slightly after stimulation, but amounts of other phospholipids were not affected.

| S-EPMC1164010 | biostudies-other

Torpedo californica electric Organ Proteome

Project description:Bottom-up proteomics and mass spectometry were applied to determine the protein repertoire of the electric organ

2011-06-23 | PRD000388 | Pride

Evolution and comparative genomics of subcellular specializations: EST sequencing of Torpedo electric organ.

Project description:Uncharacterized open reading frames (ORFs) in human genomic sequence often show a high degree of evolutionary conservation, yet have little or no tissue EST or protein data suggestive of protein product function. The encoded proteins may have highly restricted expression in specialized cells, subcellular specializations, and/or narrow windows during development. One such highly specialized and minute subcellular compartment is the neuromuscular junction (NMJ), where motorneurons contact muscle fibers. The electric Torpedo ray has evolved to expand the NMJ structure to the size of a large organ (electroplax organ), and we hypothesized that Torpedo electroplax proteins would be candidates for human ESTs expressed at the human NMJ. A total of 9719 primary electroplax cDNA clones were sequenced. We identified 44 human ORFs showing high (>63%) amino acid identity to Torpedo electroplax transcripts with enrichment for mRNA splicing motifs (SH2 and pre-mRNA splicing domains), an observation potentially important for the strict nuclear domains maintained by myonuclei underlying the NMJ. We generated antibodies against two uncharacterized human genes (C19orf29 [Drosophila cactin] and C15orf24) and showed that these were indeed expressed at the murine NMJ. Cactin, a member of the Rel transcription factor family in Drosophila, localized to the postsynaptic cytosol of the NMJ and nuclear membrane. C15orf24 protein localized to the murine postsynaptic sarcolemma. We show a novel approach towards identifying proteins expressed at a subcellular specialization using evolutionary diversity of organ function and cross-species mapping.

| S-EPMC3412124 | biostudies-literature

Isolation of pure cholinergic nerve endings from the electric organ of Torpedo marmorata.

Project description:A rapid method for the preparation of highly purified cholinergic nerve endings from the electric organ of Torpedo is described. The endings retain their cytoplasmic components, as shown by biochemical and morphological observations. The homogeneity of these synaptosomes make them a useful tool for further studies.

| S-EPMC1164206 | biostudies-other

Association of the HNK-1 epitope with 5'-nucleotidase from Torpedo marmorata (electric ray) electric organ.

Project description:5'-Nucleotidase isolated from the electric organ of the electric ray (Torpedo marmorata) has a molecular mass of 62 kDa and, on two-dimensional electrophoresis, separates into up to 13 isoforms within a pI range of 5.9-6.7. The N-terminal sequence data show a 71% identity over 17 amino acids with that previously published for the rat liver enzyme. All forms of 5'-nucleotidase are recognized by the HNK-1 monoclonal antibody. HNK-1 immunoreactivity is found at the surface of the Schwann-cell processes covering the synaptic terminals and in this respect corresponds to that of 5'-nucleotidase in the same tissue. Since a number of glycoproteins involved in cell recognition and cell adhesion carry the HNK-1 epitope, 5'-nucleotidase may play a role in cell-cell or cell-extracellular matrix interaction in addition to its activity as an enzyme.

| S-EPMC1151468 | biostudies-other

Nuclear-cytoplasmic localization of acetyl coenzyme a synthetase-1 in the rat brain.

Project description:Acetyl coenzyme A synthetase-1 (AceCS1) catalyzes the synthesis of acetyl coenzyme A from acetate and coenzyme A and is thought to play diverse roles ranging from fatty acid synthesis to gene regulation. By using an affinity-purified antibody generated against an 18-mer peptide sequence of AceCS1 and a polyclonal antibody directed against recombinant AceCS1 protein, we examined the expression of AceCS1 in the rat brain. AceCS1 immunoreactivity in the adult rat brain was present predominantly in cell nuclei, with only light to moderate cytoplasmic staining in some neurons, axons, and oligodendrocytes. Some nonneuronal cell nuclei were very strongly immunoreactive, including those of some oligodendrocytes, whereas neuronal nuclei ranged from unstained to moderately stained. Both antibodies stained some neuronal cell bodies and axons, especially in the hindbrain. AceCS1 immunoreactivity was stronger and more widespread in the brains of 18-day-old rats than in adults, with increased expression in oligodendrocytes and neurons, including cortical pyramidal cells. Expression of AceCS1 was substantially up-regulated in neurons throughout the brain after controlled cortical impact injury. The strong AceCS1 expression observed in the nuclei of CNS cells during brain development and after injury is consistent with a role in nuclear histone acetylation and therefore the regulation of chromatin structure and gene expression. The cytoplasmic staining observed in some oligodendrocytes, especially during postnatal brain development, suggests an additional role in CNS lipid synthesis and myelination. Neuronal and axonal localization implicates AceCS1 in cytoplasmic acetylation reactions in some neurons.

| S-EPMC3047483 | biostudies-literature

Purification, characterization and cellular localization of 5'-nucleotidase from Torpedo electric organ.

Project description:5'-Nucleotidase was isolated from the electric organ of the electric ray Torpedo marmorata after solubilization in Triton X-100 and deoxycholate by affinity chromatography on concanavalin A-Sepharose and AMP-Sepharose. The purified enzyme has a Km for AMP of 38 microM, with a maximal velocity of 31 units/mg of protein. Of the purine and pyrimidine mononucleotides, AMP is hydrolysed most effectively. beta-Glycerophosphate, phosphoenolpyruvate and p-nitrophenyl phosphate are not substrates for the enzyme. Adenosine 5'-[alpha, beta-methylene]diphosphate, ADP and ATP are competitive inhibitors in this order of potency. Concanavalin A inhibits enzyme activity in a non-competitive manner. Whereas Mg2+, Ca2+ and Sr2+ activate enzyme activity in the millimolar range, Hg2+, and in particular Pb2+ and Zn2+, inhibit enzyme activity. On SDS/polyacrylamide-gel electrophoresis the enzyme has an apparent Mr of 62000, whereas that of the native deoxycholate-enzyme complex is 131000. An antiserum raised against the native enzyme inhibits enzyme activity. Inhibition studies suggest the presence of tissue-specific variants of the enzyme. By immunohistochemical analysis the enzyme can be localized to the ramifications of nerve terminals in the electric organ.

| S-EPMC1148201 | biostudies-other

The metabolism of neuropeptides. Both phosphoramidon-sensitive and captopril-sensitive metallopeptidases are present in the electric organ of Torpedo marmorata.

Project description:A membrane fraction from the electric organ of Torpedo marmorata hydrolyses the Gly3-Phe4 bond of [D-Ala2, Leu5]enkephalin as well as the Gly-His bond of benzoyl-Gly-His-Leu. The hydrolysis of benzoyl-Gly-His-Leu is completely inhibitable by Captopril (I50 = 19nM), consistent with peptidyl dipeptidase activity, but enkephalin hydrolysis is inhibited to a maximum of only 70%. The residual activity hydrolysing enkephalin is inhibited by phosphoramidon (I50 = 15nM) and therefore resembles endopeptidase-24.11, a mammalian plasma-membrane enzyme implicated in the metabolism of neuropeptides. Both enkephalin-hydrolysing activities in Torpedo electric organ are inhibited by 1,10-phenanthroline, like their mammalian counterparts. The peptidases may function in the hydrolysis of endogenous peptides or in neurotransmitter exocytosis in the electric organ.

| S-EPMC1144167 | biostudies-other

Soluble low-Km 5'-nucleotidase from electric-ray (Torpedo marmorata) electric organ and bovine cerebral cortex is derived from the glycosyl-phosphatidylinositol-anchored ectoenzyme by phospholipase C cleavage.

Project description:Soluble and membrane-bound low-Km 5'-nucleotidase was isolated from high-speed supernatants and membrane fractions derived from the electric organ of the electric ray (Torpedo marmorata) or from bovine brain cerebral cortex. Purification of both enzymes included chromatography on concanavalin A-Sepharose and AMP-Sepharose. The contribution to the total of soluble enzyme activity was lower in electric organ (1.6%) than in bovine cerebral cortex (27.9%). Membrane-bound and soluble forms have very similar Km values for AMP and are inhibited by micromolar concentrations of ATP. Both forms cross-react with, and are inhibited by, an antibody against the membrane-bound surface-located (ecto-) 5'-nucleotidase from electric organ. The HNK-1 carbohydrate epitope is present on both forms of the Torpedo enzyme, but is entirely absent from bovine cerebral-cortex 5'-nucleotidase. An antibody specific for the inositol 1,2-(cyclic)monophosphate that is formed on phospholipase C cleavage of an intact glycosyl-phosphatidylinositol (GPI) anchor binds to the soluble, but not to the membrane-bound, form of the enzyme from both sources. Our results suggest that soluble low-Km 5'-nucleotidase in both electric organ and bovine brain is derived from the membrane-bound GPI-anchored form of the enzyme by the action of a phospholipase C and is not a soluble cytoplasmic enzyme.

| S-EPMC1132579 | biostudies-other

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