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PubMed1985

Central GABA-ergic mechanism in stress-induced gastric ulceration.

The effect of exogenous administration of central amino acid neurotransmitters gamma-aminobutyric acid (GABA), glycine, glutamic acid and aspartic acid) into the cerebroventricular system was studied on gastric ulceration induced in albino rats either by 2 h restraint at 4 degrees C or by 6 h restraint at room temperature (30 +/- 2 degrees C). GABA (5, 10, 20 and 50 micrograms) injected intracerebroventricularly (i.c.v.) showed a dose-dependent reduction of gastric ulceration induced by 2 h restraint at 4 degrees C (CRU), whereas glycine (5, 10 and 20 micrograms i.c.v.) failed to alter this response. Muscimol (5 and 10 micrograms i.c.v.), a GABA agonist, and sodium valproate (400 mg kg-1 p.o.), which increases the concentration of GABA in the CNS, significantly reduced CRU. Pretreatment with the GABA antagonists, bicuculline (40 micrograms i.c.v.) or picrotoxin (5 micrograms i.c.v.) reversed the anti-ulcerogenic effects of GABA (50 micrograms i.c.v.) and sodium valproate (400 mg kg-1 p.o.). Bicuculline (20 and 40 micrograms i.c.v.) and picrotoxin (5 and 10 micrograms i.c.v.) per se did not induce gastric ulceration in normal rats but significantly enhanced the minimal ulcerogenic response induced by 6 h restraint at room temperature. Pretreatment with GABA (i.c.v.) significantly reduced the gastric ulceration induced by i.c.v. administration of acetylcholine and adrenaline or pylorus ligation. Glutamic acid (20 micrograms i.c.v.) and aspartic acid (20 micrograms i.c.v.) did not significantly enhance the minimal ulcerogenic response induced by 6 h restraint at room temperature. These observations show that GABA in the CNS exerts an inhibitory effect on stress-induced ulcerogenesis.

Acetylcholine↗
PubMed1993

Changes of amino acid and monoamine levels after neonatal 6-hydroxydopamine denervation in rat basal ganglia, substantia nigra, and Raphe nuclei.

The effects of a neonatal dopaminergic deafferentation with the neurotoxin 6-hydroxydopamine (6-OHDA) on endogenous tissue levels of catecholamines, indoleamines, and amino acids were investigated in discrete rat brain regions. After producing the lesion at postnatal day 3 by intraventricular injections of 6-OHDA, with a desipramine pretreatment to protect noradrenaline neurons, the animals were kept for 3 months. Their brains were dissected to obtain samples of neostriatum, Globus pallidus, Substantia nigra, and Raphe nuclei, which were then analyzed by high-performance liquid chromatography, coupled either to electrochemical detection for aromatic monoamines, or to post-column ninhydrin derivatization with spectrophotometry for amino acids. The neonatal 6-OHDA treatment depleted dopamine (DA) levels in neostriatum, Globus pallidus, and Substantia nigra, but in Raphe nuclei DA was increased. The main metabolites of DA were also decreased in neostriatum, Globus pallidus, and Substantia nigra but remained unchanged in Raphe nuclei. Serotonin (5-HT) and its metabolite 5-hydroxy-indole-3-acetic acid increased in neostriatum and Raphe nuclei; in Substantia nigra there was a slight increase in 5-HT only. The 6-OHDA lesion caused heterogeneous alterations in amino acid contents, which varied according to the region. In the neostriatum there were increases of gamma-aminobutyric acid (GABA), aspartic acid, and glycine. In the Globus pallidus taurine, GABA, glutamic acid, glutamine, aspartic acid, serine, and alanine were elevated. In the Substantia nigra only increases in taurine, GABA, glutamic acid, and glutamine could be documented. This study shows important changes in amino acid levels and in some of their ratios, occurring in different anatomical subdivisions of the basal ganglia and related brainstem nuclei following a neonatal treatment with 6-OHDA. The results thus demonstrate major biochemical modifications in amino acids in the aftermath of a DA denervation and/or a 5-HT hyperinnervation during an early developmental period.

Amino Acids↗
PubMed1978

Speculations on the evolution of the genetic code. II.

An evolutionary scheme is postulated in which a primitive code, involving only guanine and cytosine, would code for glycine (GG), alanine (GC), arginine (CG) and proline (CC). From each of these amino acids and their codons, there evolves a family of related amino acids as the code expands. The four families are: (1) alanine valine, leucine, isoleucine, phenylalanine, tyrosine, methionine and tryptophane; (2) proline, threonine and serine; (3) arginine, lysine, and histidine; (4) glycine, serine cysteine, glutamic acid, glutamine, aspartic acid and asparagine. Except for the glycine relation to glutamic acid and aspartic acid, all amino acids are related by chemical similarities in their side chains. Glycine not having a side chain would permit a more complex set of substitutions.

Amino Acids↗
PubMed1992

Protective effect of vinconate on ischemia-induced neuronal damage in the rat hippocampus.

The protective effect of vinconate, a vinca alkaloid derivative, on ischemia-induced neuronal damage was investigated using a model of rat forebrain ischemia caused by occlusion of four vessels. Hippocampal cell loss was observed histologically and neurochemically 5 days after 10 min of ischemia. Treatment with vinconate (50 and 200 mg/kg i.p.) before cerebral ischemia significantly suppressed neuronal cell loss in the hippocampal CA1 region and the decrease in the content of neuroactive amino acids in the hippocampus. The release of neuroactive amino acids in the hippocampus was significantly increased by cerebral ischemia. Pretreatment with vinconate (50 and 200 mg/kg i.p.) significantly attenuated the increased release of glutamic acid and aspartic acid, but not the release of gamma-aminobutyric acid (GABA), taurine and glycine. This suppressive effect of vinconate was antagonized by scopolamine (10(-5) M). The addition of vinconate (10(-11)-10(-4) M) had no effect on the binding of [3H]MK-801. These results indicate that pretreatment with vinconate attenuates the ischemia-induced release of excitatory amino acids into the extracellular space of the hippocampus via the stimulation of presynaptic muscarinic acetylcholine receptors. The present results also suggest that this suppressive effect of vinconate on the release of excitatory amino acids (glutamic acid and aspartic acid) may play a crucial role in the protective action of this agent against ischemia-induced neuronal damage in the hippocampus.

Amino Acids↗
PubMed1992

Purification, characterization and gene cloning of a novel glutamic acid-specific endopeptidase from Staphylococcus aureus ATCC 12600.

Twenty strains of Staphylococcus aureus from ATCC type cultures and strains found in clinical studies were cultivated, and their endopeptidase activity specific for glutamic acid was surveyed using benzyloxycarbonyl-Phe-Leu-Glu-p-nitroanilide (Z-Phe-Leu-Glu-pNA) as a substrate. The activity was found in two of the strains, ATCC 12600 and ATCC 25923. A glutamic acid-specific proteinase, which we propose to call SPase, was purified from the culture filtrate of S. aureus strain ATCC 12600 by a series of column chromatographies on DEAE-Sepharose twice and on Sephacryl S-200. A single band was observed on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the purified SPase. The molecular weight of the proteinase was estimated to be 34000 by SDS-PAGE. When synthetic peptides and oxidized insulin B-chain were used as substrates, SPase showed the same substrate specificity as V8 proteinase, EC 3.4.21.9, which specifically cleaves peptide bonds on the C-terminal side of glutamic acid and aspartic acid. Examination with p-nitroanilides of glutamic acid and aspartic acid as substrates, however, revealed that both proteinases are highly specific for a glutamyl bond in comparison with an aspartyl bond. To elucidate the complete primary structure of SPase, its gene was cloned from genomic DNA of S. aureus ATCC 12600, and the nucleotide sequence was determined. Taking the amino acid sequence of SPase from the NH2-terminus to the 27th residue into consideration, the clones encode a mature peptide of 289 amino acids, which follows a prepropeptide of 68 residues. SPase was confirmed to be a novel endopeptidase specific for glutamic acid, being different from V8 proteinase which consists of 268 amino acids.

Amino Acid Sequence↗
PubMed1993

Enzymatic activity of poliovirus RNA polymerases with mutations at the tyrosine residue of the conserved YGDD motif: isolation and characterization of polioviruses containing RNA polymerases with FGDD and MGDD sequences.

The poliovirus RNA-dependent RNA polymerase (3Dpol) shares a region of homology with all RNA polymerases, centered around the amino acid motif YGDD, which has been postulated to be involved in the catalytic activity of the enzyme. Using oligonucleotide site-directed mutagenesis, we substituted the tyrosine at this motif of the poliovirus RNA-dependent RNA polymerase with cysteine, histidine, isoleucine, methionine, phenylalanine, or serine. The enzymes were expressed in Escherichia coli, and in vitro enzyme activity was tested. The phenylalanine and methionine substitutions resulted in enzymes with activity equal to that of the wild-type enzyme. The cysteine substitution resulted in an enzyme with approximately 50% of the wild-type activity, while the serine substitution resulted in an enzyme with approximately 10% of the wild-type activity; the isoleucine and histidine substitutions resulted in background levels of enzyme activity. To assess the effects of the mutants in viral replication, the mutant polymerase genes were subcloned into the infectious cDNA clone of poliovirus. Transfection of poliovirus cDNA containing the phenylalanine mutation in 3Dpol gave rise to virus in all of the transfection trials, while cDNA containing the methionine mutation resulted in virus in only 3 of 40 transfections. Transfection of cDNAs containing the other substitutions at the tyrosine residue did not result in infectious virus. The recovered viruses demonstrated kinetics of replication similar to those of the wild-type virus, as measured by [3H]uridine incorporation at either 37 or 39 degrees C. RNA sequence analysis of the 3Dpol gene of both viruses demonstrated that the tyrosine-to-phenylalanine or tyrosine-to-methionine mutation was still present. No other differences in the 3Dpol gene between the wild-type and phenylalanine-containing virus were found. The virus containing the methionine mutation also contained two other nucleotide changes from the wild-type 3Dpol sequence; one resulted in a glutamic acid-to-aspartic acid change at amino acid 108 of the polymerase, and the other resulted in a C-to-T base change at nucleotide 6724, which did not result in an amino acid change. To confirm that the second amino acid mutation found in the 3Dpol gene of the methionine-substituted virus allowed for replication ability, a mutation corresponding to the glutamic acid-to-aspartic acid change was made in the polymerase containing the methionine substitution, and this double-mutant polymerase was expressed in E. coli. The double-mutant enzyme was as active as the wild-type enzyme under in vitro assay conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1978

The production of extracellular amino acids by rumen bacteria.

One hundred and sixteen freshly isolated rumen bacteria and 10 laboratory strains were studied for the production and excretion of free amino acids during growth in a basal medium containing glucose, cellobiose, and soluble starch as the energy sources, (NH4)2SO4 as the prime nitrogen source, volatile fatty acids, hemin, vitamins, Na2CO3, and cysteine as the reducing agent. Amino acid analyses of 48-h culture fluids of the isolates indicated the presence of alanine, glutamic acid, valine, aspartic acid, glycine, serine, lysine, methionine, leucine, isoleucine, threonine, histidine, arginine, phenylalanine, and tyrosine. Most isolates excreted some free amino acids. Alanine, glutamic acid, valine, aspartic acid, and glycine were found in the greatest concentrations with some isolates accumulating between 50 and 295 microgram/ml of one or more of these compounds. Concentrations of the remaining amino acids rarely exceeded 20 microgram/ml of culture fluid. Growth studies demonstrated that the amino acids were excreted during active growth of the bacteria and ceased shortly after growth became limited.

Amino Acids↗
PubMed1983

The importance of dietary amino acids on the reproduction and longevity of adult Dacus oleae (Gmelin) (Diptera Tephritidae).

When the amino-acid mixture of an effective chemically defined diet was replaced by single amino acids, keeping the total nitrogen at the same level, the egg production of Dacus oleae was minimal with all the 19 amino acids tested. Male survival was adversely affected by the amino acids : alanine, aspartic acid, glutamic acid, glycine, hydroxyproline, lysine, serine and tyrosine, while female survival was shortened when the amino acids : glycine, hydroxyproline and lysine were added. The creation of amino-acid imbalances, by deleting the 19 amino acids individually, from the complete amino-acid mixture, showed that the amino acids : arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, serine, threonine, tryptophane and valine were indispensable to the adult Dacus oleae flies, as far as egg production is concerned. Survival of the male flies was significantly shortened when the amino acids : alanine, hydroxyproline and tryptophane were omitted. Significant differences in longevity between males and females were scored, when the amino acids : alanine, aspartic acid, cystine, glycine and tryptophane, were omitted.

Amino Acids↗
PubMed1994

Effects of apomorphine and L-methionine sulphoximine on the release of excitatory amino acid neurotransmitters and glutamine in the striatum of the conscious rat.

The effects of apomorphine, a D1-, D2-dopamine receptor agonist, on the extracellular concentrations of excitatory amino acids, glutamic and aspartic acids, and on that of their precursor, glutamine, were investigated using an intracerebral perfusion system. Apomorphine produced a concentration-related rise in glutamic acid concentration in cerebral perfusates (P < 0.01) whereas only the highest concentration of apomorphine (3 x 10(-3) micrograms/microliters) increased the concentration of aspartic acid (P < 0.05). These effects were seen in the sample taken at the same time as the apomorphine injection. The rise in glutamine concentration (P < 0.01) produced by apomorphine continued for 10 min beyond perfusion with apomorphine. These effects were attenuated by previous injections of D1-, D2-dopamine receptor blocker. To investigate further the release of glutamine, the glutamine synthetase inhibitor L-methionine sulphoximine (MSO) was injected intracerebrally before apomorphine perfusion. After MSO pre-injection, the extracellular concentration of glutamine decreased (P < 0.01) to near zero concentrations. In MSO-treated animals, apomorphine did not induce the release of glutamic acid, aspartic acid or glutamine. These results indicate a role for dopamine in the release of excitatory amino acids and glutamine in the neostriatum of the rat. A possible volumetric interaction between dopamine and glutamic acid as well as the hypothesis of a striato-pallido-thalamo-cortico-striatal feedback loop are discussed.

Analysis of Variance↗
PubMed2002

Implication of p53 and caspase-3 in kainic acid but not in N-methyl-D-aspartic acid-induced apoptosis in organotypic hippocampal mouse cultures.

Apoptotic death is known to be an active process requiring the activation of several apoptotic proteins. Depending on the tissue studied and the stimulus used, these processes are distinct. In this work, we studied if there is a putative implication of the p53 and the caspase-3 proteins in kainic acid (KA) and N-methyl-D-aspartic acid (NMDA)-induced apoptosis in organotypic cultures and if there is any relationship between their respective expressions. We found that KA and NMDA both induce apoptosis but only KA-induced apoptosis is p53- and caspase-3-dependent. This demonstrates that KA and NMDA induce apoptosis following different intracellular pathways.

Animals↗
PubMed1986

Post-translational methylation of asparaginyl residues. Identification of beta-71 gamma-N-methylasparagine in allophycocyanin.

A novel post-translationally modified residue, gamma-N-methylasparagine, was detected in the beta subunit of Anabaena variabilis allophycocyanin. Structure determination was accomplished by isolating a decapeptide, AP-beta (63-72) shown to have the following structure: Ser-Asp-Ile-Thr-Arg-Pro-Gly-Gly- Asn[N-CH3]-homoserine lactone Fast atom bombardment-mass spectrometry established that the residue corresponding to position 71 in the protein (DeLange, R. J., Williams, L. C., and Glazer, A. N. (1981) J. Biol. Chem. 256, 9558-9566) contained 13 mass units more than expected for aspartic acid though aspartic acid was recovered after acid hydrolysis. The 1H NMR spectrum of AP-beta (63-72) revealed a strong methyl single at 2.71 ppm characteristic of the methyl derivative of an amide nitrogen. Confirmation of this bond arrangement was obtained by detection of a stoichiometric amount of methylamine in acid hydrolysates of the peptide. This is the first report of gamma-N-methylasparagine in a protein. Amino acid analysis of A. variabilis allophycocyanin subunits showed that the derivative at position 71 can account for the total methylamine released from the beta subunit, while hydrolysis of the alpha subunit released no methylamine. The beta subunits of the allophycocyanins from the cyanobacterium Synechococcus PCC 6301 and the red alga Porphyridium cruentum each released 1 eq of methylamine upon acid hydrolysis. No methylamine was released from the alpha subunits.

Amino Acid Sequence↗
PubMed1997

N-methyl-D-aspartic acid-induced penile erection and yawning: role of hypothalamic paraventricular nitric oxide.

A dose of N-methyl-D-aspartic acid (NMDA, 50 ng) that induces penile erection and yawning when injected into the paraventricular nucleus of the hypothalamus, increased the concentration of NO2- from 1.10 +/- 0.28 microM to 7.32 +/- 1.12 microM and of NO3 from 4.96 +/- 0.69 microM to 10.5 +/- 1.61 microM in the paraventricular dialysate obtained from male rats by in vivo microdialysis. NO2- concentration was not increased by (+/-)-alpha-(amino)-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA, 100 ng) or by trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD) (100 ng), which were unable to induce these behavioral responses. N-Methyl-D-aspartic acid effect on NO2- concentration, penile erection and yawning was prevented by dizolcipine (MK-801) (10-100 ng) or by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (20 microg), but not by the oxytocin receptor antagonist [d(CH2)5,Tyr(Me)2,Orn8]vasotocin (100 ng), or by the guanylate cyclase inhibitor methylene blue (20 microg) given in the paraventricular nucleus 15 min before N-methyl-D-aspartic acid or by the dopamine receptor antagonist haloperidol (0.5 mg/kg) given intraperitoneally 30 min before N-methyl-D-aspartic acid. In contrast, the nitric oxide scavenger hemoglobin (20 microg) given in the paraventricular nucleus prevented N-methyl-D-aspartic acid-induced NO2- concentration increase, but was unable to prevent penile erection and yawning. The results suggest that N-methyl-D-aspartic acid induces penile erection and yawning by increasing nitric oxide synthase activity in the paraventricular nucleus of the hypothalamus, possibly in the cell bodies of oxytocinergic neurons projecting to extra-hypothalamic brain areas and mediating these behavioral responses.

Animals↗
PubMed1991

Effect of single amino acid substitutions at positions 49 and 60 on the thermal unfolding of the tryptophan synthase alpha subunit from Salmonella typhimurium.

We have used circular dichroism measurements to compare the thermal unfolding of the wild type tryptophan synthase alpha subunit from Salmonella typhimurium with that of seven mutant forms with single amino acid replacements at two active site residues. Glutamic acid 49 has been replaced by phenylalanine, glutamine, or aspartic acid. Aspartic acid 60 has been replaced by alanine, aspartic acid, asparagine, or tyrosine. Thermodynamic properties (delta G, delta H, delta S, and Tm) of the wild type and mutant forms have been determined experimentally by measuring the free energy of unfolding as a function of temperature. Increasing the pH from 7.0 to 8.8 decreases the tm of the wild type alpha subunit from 56 to 45 degrees C. The thermal unfolding of the wild type alpha subunit and of six of the seven mutant forms can be described as reversible, two-state transitions. In contrast, the melting curve of a mutant alpha subunit in which aspartic acid 60 is replaced by tyrosine indicates the presence of a folding intermediate which may correspond to a "molten globule." Correlations between our observations and previous folding studies and the X-ray crystallographic structure are presented. Substitution of glutamic acid 49, which is located in the hydrophobic "pit" of an eight-fold alpha/beta barrel, by a hydrophobic phenylalanine residue increases the tm from 56 to 60 degrees C. In contrast, replacement of aspartic acid 60, which is accessible to solvent, results in small reductions in the thermal stability.

Circular Dichroism↗
PubMed1988

Voltage-dependent block by strychnine of N-methyl-D-aspartic acid-activated cationic channels in rat cortical neurons in culture.

Single-channel currents were recorded by means of the patch clamp method in outside-out patches excised from rat cortical neurons in primary culture. The excitatory amino acid N-methyl-D-aspartic acid activated mainly 40-50 pS conductance channels. Channel opening durations were characterized by a series of rapid openings and closures induced by the presence of Mg2+ ions. This inhibitory effect was voltage dependent. Strychnine, the antagonist of the glycine-gated Cl- channels, blocks the N-methyl-D-aspartic acid-activated cationic channel in cultured rat cortical neurons. Strychnine action is voltage dependent and it is not counteracted by ethylenediaminetetraacetic acid, ruling out Mg2+ contamination of strychnine. It has been reported recently that glycine increases the rate of openings of N-methyl-D-aspartic acid-activated channels. This action is not affected by the presence of strychnine. Our results show that 1) Mg2+ and strychnine have an apparently similar intermediate blocking action on the NMDA-activated channels, 2) strychnine presumably acts as a sequential open channel blocker producing a different type of block compared with the one reported for Mg2+ ions, and 3) the lack of effect of strychnine on the glycine potentiation of the N-methyl-D-aspartic acid response indicates that this alkaloid does not competitively antagonize glycine but acts as an open channel blocker.

Allosteric Regulation↗
PubMed1983

Characterisation of the cross-reacting carbohydrate groups on two variant surface glycoproteins of Trypanosoma brucei.

The nature of the cross-reacting groups on two variant surface glycoproteins of Trypanosoma brucei has been investigated after isolation of glycopeptides produced by extensive proteolytic digestion of the proteins. One variant yielded two glycopeptides after pronase digestion, one of which was the glycosylated C-terminal aspartic acid. In a second variant there are two carbohydrate groups close to the C-terminus. Considerable heterogeneity in the size of the sugar attached to an asparagine residue was detected whereas the C-terminal serine was glycosylated but showed no size heterogeneity. For both variants it was shown that the C-terminal glycosylated amino acid (either aspartic acid or serine) was responsible for the immunological cross-reaction between distinct variant glycoproteins. The stability of the cross-reacting determinant was also investigated.

Amino Acids↗
PubMed1992

Increased plasma glutamic acid in a genetic model of epilepsy.

A significant increase in the plasma levels of glutamic acid and a significant decrease in aspartic acid and taurine in epileptic patients and their first degree relatives was reported more than a decade ago and an underlying genetic basis for these amino acid changes was suggested. The main objective of the present study was to determine the plasma levels of glutamic acid, aspartic acid and taurine in El mice which are an inbred epileptic mutant mouse strain. The results show a significant increase in plasma glutamic acid but no changes in aspartic acid or taurine in the epileptic mice as compared to controls. The data provide the first evidence of a significant increase in plasma glutamic acid in an animal model of hereditary epilepsy and substantiate the hypothesis that a genetic defect underlies the elevated plasma glutamic acid levels in association with epilepsy. The findings are also compatible with neurochemical and neurophysiological evidence implicating glutamic acid in the mechanism of seizures.

Animals↗
PubMed1987

Features of amino acid metabolism in Moniliformis moniliformis (Acanthocephala) in vitro.

Experiments to investigate the metabolism of glycine, L-glutamic acid and L-aspartic acid by Moniliformis moniliformis were carried out by incubating adult worms aerobically for 3 h at 37 degrees C in Tyrode's solution containing either [U-14C]glycine, L-[U-14C]glutamic acid, L-[U-14C]aspartic acid or L-[4-14C]aspartic acid. Much of the glycine and glutamic acid was absorbed by the worms, but little of either was metabolized. Aspartic acid was readily taken up and metabolized. After incubating with L[U-14C]aspartic acid, most radioactivity was found in ethanol and a volatile compound, presumed to be carbon dioxide, with smaller amounts in lactate, alanine, acetate, malate, glucose and succinate. After incubating with L-[4-14C]aspartic acid, most radioactivity was found in lactate and the presumed CO2 with small amounts in alanine, malate and succinate. No radioactivity was found associated with ethanol or acetate. Possible metabolic pathways and suggestions for a relationship between the metabolism of aspartate with that of alanine and serine in this parasite are discussed.

Acanthocephala↗