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PubMed1988

Resolution of alpha-substituted amino acid enantiomers by high-performance liquid chromatography after derivatization with a chiral adduct of o-phthalaldehyde. Application to glutamic acid analogues.

The fluorescent diastereoisomeric adducts formed in a precolumn derivatization reaction of enantiomeric alpha-substituted amino acids with o-phthalaldehyde and N-acetyl-L-cysteine were separated by high-performance liquid chromatography on a conventional reversed-phase column. This method was particularly efficient for the complete analytical resolution of alpha-substituted glutamic acid analogues, such as 2-methylglutamic acid, and several cyclic analogues (1-amino-1,3-dicarboxycyclohexane, 1-amino-1,3-dicarboxy-2-cyclohexene and 1-amino-1,3-dicarboxycyclopentane). The order of elution from the column was correlated with the absolute configuration of the derivatives.

Amino Acids↗
PubMed1976

The biosynthesis of delta-aminolevulinic acid from the intact carbon skeleton of glutamic acid in greening barley.

The formation of delta-aminolevulinic acid in mammals birds, yeast and some bacteria is known to take place by the ALA-synthetase assisted coupling of glycine with succinylCoA. Plants, however, form the bulk of their delta-aminolevulinate in another way. We present evidence here that the intact, 5-carbon chain of glutamate becomes that of delta-aminolevulinate. Greening barley was fed specifically labelled glutamate and levulinate to create a pool of labelled delta-aminolevulinate. Levulinate, a competitive inhibitor of ALA-dehydratase, prevents the metabolism of delta-aminolevulinate. The carbon chain of the labelled delta-aminolevulinate was broken into formaldehyde and succinate by periodate to determine the position of the label. It was found that the C1, carboxyl carbon of glutamate becomes the amino-bearing (C5) carbon of delta-aminolevulinate and forms the formaldehyde on cleavage. delta-Aminolevulinate formed from C3,4-labelled glutamate bears its label in the succinate cleaved fragment. We conclude that during the light induced development of the plastid in barley the carbon chain of delta-aminolevulinate is formed from the intact chain of glutamate. ALA-synthetase catalyzed the formation of delta-aminolevulinate from glycine and succinylCoA cannot play a quantitively important role in the formation of chlorophyll.

Aminolevulinic Acid↗
PubMed1976

Effects of intracisternal GABA or glutamic acid upon behavioral activity in the rat.

It has been postulated that GABA acts as an inhibitor of command neurons, the activity of which initiates behavior. A prediction of this hypothesis is that elevations in functional GABA levels in the brain will cause decreases in behavioral output. Accordingly, in this study rats were injected intracisternally with either saline or one micromole of GABA or its excitatory precursor, glutamic acid, and behavioral activity in a novel environment was recorded as it habituated over the course of the subsequent 4 hours. The activity of the animals that were injected with GABA was greatly decreased, while the activity of the animals that were injected with glutamic acid was apparently unaffected, as compared to animals given saline. These data provide support for the hypothesis that GABA functions as an inhibitory neurotransmitter for behavior-activating command neurons.

Aminobutyrates↗
PubMed1974

Antibody response of inbred mouse strains to ordered tetrapeptides of tyrosine and glutamic acid attached to multichain polyalanine or polyproline. Tyr-Tyr-Glu-Glu is a major determinant of the random poly-(Tyr, Glu)-polyDLAla--polyLys.

Five inbred mouse strains which represent high and low responders to the random synthetic polypeptide poly(LTyr,LGlu)-polyDLAla--polyLLys, designated (T, G)-A--L, to which the immune response is controlled by an H-2-linked gene, were immunized with three ordered tetrapeptides composed of tyrosine and glutamic acid attached either to multichain poly-DL-alanine or to polyproline. Only one of the three antigenic determinants, namely tyrosyl-tyrosyl-glytamyl-glutamic acid (T-T-G-G), resembled the random peptide (T, G) in the pattern of immune responses elicited against it, and in the cross-reactivity of the specific antibodies with (T, G)-A--L. The immune response pattern to the other two ordered tetrapeptides, T-G-T-G and G-T-T-G, was different from that obtained with (T, G)-A--L, and no cross-reactivity was detected between the antibodies provoked with these peptides and (T, G)-A--L. Thus, it is suggested that T-T-G-G is a major determinant in the random (T, G)-A--L.

Alanine↗
PubMed1998

Decrease in glutamic acid decarboxylase level in the hypothalamus of spontaneously hypertensive rats.

BACKGROUND: A reduction in gamma-aminobutyric (GABA)-mediated inhibition of pressor sites in the caudal hypothalamus of spontaneously hypertensive rats compared with that of normotensive Wistar-Kyoto rats has recently been demonstrated. OBJECTIVE: To determine whether the reduction in GABA-mediated inhibition of the caudal hypothalamus of the spontaneously hypertensive rats results from reductions both in the number of GABA-synthesizing neurons and in the amount of the GABA-synthesizing enzyme, glutamic acid decarboxylase messenger RNA (mRNA). DESIGN AND METHODS: A polyclonal antibody (Chemicon) for the 67 kDa isoform of glutamic acid decarboxylase (GAD67) was used to immunocytochemically label GABAergic neurons in the caudal hypothalamus of spontaneously hypertensive and Wistar-Kyoto rats that had been treated beforehand with colchicine. The labeled cells were counted for both strains by a blinded analysis and compared. Caudal hypothalamic tissues from spontaneously hypertensive and Wistar-Kyoto rats were analysed for GAD67 mRNA by Northern blotting. The signal intensities of the radioactive probe specific for GAD67 for the two strains were analyzed by using a phosphorimager and compared. Control areas for the immunocytochemical (zona incerta) and Northern blotting (cortex, midbrain, cerebellum, and brain stem) experiments were used to determine regional differences in expression of GAD67. RESULTS: Both the hypothalamus and cerebellum of spontaneously hypertensive and Wistar-Kyoto rats contained GAD67-immunoreactive neurons; however, there were 42% fewer GAD67 neurons in the caudal hypothalamus of spontaneously hypertensive rats than there were in that of Wistar-Kyoto rats. Furthermore, a 33% reduction in the amount of GAD67 messenger RNA in the caudal hypothalamus of spontaneously hypertensive rats compared with that for Wistar-Kyoto rats was demonstrated. Analysis of the expression of GAD67 in the cortex, midbrain, cerebellum, brain stem, and total brain revealed no difference between spontaneously hypertensive and Wistar-Kyoto rats. CONCLUSIONS: Our findings demonstrate that the spontaneously hypertensive rat has fewer neurons synthesizing GABA and less GAD67 mRNA in the caudal hypothalamus than do Wistar-Kyoto rats. This deficit in the GABAergic system in the caudal hypothalamus, a well-known cardiovascular regulatory site, could contribute to the essential hypertension in this animal model.

Animals↗
PubMed2004

Synthesis and characterization of branched poly(L-glutamic acid) as a biodegradable drug carrier.

Polymeric drug delivery systems are used not only to improve aqueous solubility of drug molecules but also to achieve desirable pharmacokinetics and an enhanced therapeutic index. New biodegradable polymers are needed to improve the biodistribution and targeting-ability of polymeric carriers. In this study, the synthesis and characterization of branched poly(L-glutamic acid) (PG) containing multiple PG chains centered on a poly(amidoamine) (PAMAM) dendrimer or polyethyleneimine (PEI) cores were described. The branched PG polymers were obtained by ring-opening polymerization of benzyl ester of L-glutamic acid N-carboxyanhydride using PAMAM or PEI as the initiator. These polymers were degradable in the presence of the lysosomal enzyme cathepsin B, albeit more slowly than linear PG. Unlike conventional linear PG, each branched PG possessed multiple terminal amino groups. This made it possible to attach multiple targeting moieties selectively to the termini of branched PG. Conjugation of monofunctional or heterodifunctional polyethylene glycol to the chain ends of branched PG was demonstrated in the presence of side chain carboxyl groups. Furthermore, folic acid, a model targeting moiety, and the near-infrared dye indocyanine green, a model diagnostic agent, were successfully conjugated to the terminal amino groups and the side chain carboxyl groups of branched PG, respectively. The resulting conjugate had reduced nonspecific interaction and bound selectively to tumor cells expressing folate receptors. Thus, branched PG may be useful as a polymeric carrier for targeted drug delivery.

Cell Line, Tumor↗
PubMed1980

Effect of oral monosodium glutamate on glutamic acid levels in the nucleus arcuatus of the hypothalamus and on serum osmolality of adult and infant mice.

Monosodium glutamate (MSG) given by gavage to 7-day-old mice at 2 g/kg body weight (b.wt.) as a 20% solution w/v resulted in a 27% increase in the glutamic acid (GA) content in the nucleus arcuatus of the hypothalamus (NAH). When MSG was administered by gavage to adult mice at 4 g/kg b.wt. as a 20% solution w/v, GA levels in NAH remained unchanged. Serum osmolality, measured after oral MSG, was elevated in infant mice but was unaffected in adults.

Animals↗
PubMedDate not supplied

Synthesis of potent inhibitors of anthrax toxin based on poly-L-glutamic acid.

We report the synthesis of biodegradable polyvalent inhibitors of anthrax toxin based on poly-L-glutamic acid (PLGA). These biocompatible polyvalent inhibitors are at least 4 orders of magnitude more potent than the corresponding monovalent peptides in vitro and are comparable in potency to polyacrylamide-based inhibitors of anthrax toxin assembly. We have elucidated the influence of peptide density on inhibitory potency and demonstrated that these inhibitory potencies are limited by kinetics, with even higher activities seen when the inhibitors are preincubated with the heptameric receptor-binding subunit of anthrax toxin prior to exposure to cells. These polyvalent inhibitors are also effective at neutralizing anthrax toxin in vivo and represent attractive leads for designing biocompatible anthrax therapeutics.

Absorbable Implants↗
PubMed2003

Examining the role of glutamic acid 183 in chloroperoxidase catalysis.

Site-directed mutagenesis has been used to investigate the role of glutamic acid 183 in chloroperoxidase catalysis. Based on the x-ray crystallographic structure of chloroperoxidase, Glu-183 is postulated to function on distal side of the heme prosthetic group as an acid-base catalyst in facilitating the reaction between the peroxidase and hydrogen peroxide with the formation of Compound I. In contrast, the other members of the heme peroxidase family use a histidine residue in this role. Plasmids have now been constructed in which the codon for Glu-183 is replaced with a histidine codon. The mutant recombinant gene has been expressed in Aspergillus niger. An analysis of the produced mutant gene shows that the substitution of Glu-183 with a His residue is detrimental to the chlorination and dismutation activity of chloroperoxidase. The activity is reduced by 85 and 50% of wild type activity, respectively. However, quite unexpectedly, the epoxidation activity of the mutant enzyme is significantly enhanced approximately 2.5-fold. These results show that Glu-183 is important but not essential for the chlorination activity of chloroperoxidase. It is possible that the increased epoxidation of the mutant enzyme is based on an increase in the hydrophobicity of the active site.

Aspergillus niger↗
PubMed2001

Chiral analysis of UV nonabsorbing compounds by capillary electrophoresis using macrocyclic antibiotics: 1. Separation of aspartic and glutamic acid enantiomers.

Glycopeptide antibiotics, namely vancomycin or teicoplanin, were evaluated in capillary electrophoresis for the analysis of UV nonabsorbing compounds such as aspartic and glutamic acid enantiomers. Electrophoretic runs were performed in laboratory-made polyacrylamide-coated capillaries using the partial filling-counter current method in order to avoid the presence on the detector path of the absorbing chiral selector. The background electrolyte consisted of an aqueous or aqueous-organic buffer in the pH range of 4.5-6.5 of sorbic acid/histidine and the appropriate concentration of chiral selector. Several experimental parameters such as antibiotic concentration and type, buffer pH, organic modifier, type and concentration of absorbing co-ion (for the indirect UV detection) were studied in order to find the optimum conditions for the chiral resolution of the two underivatized amino acids in their enantiomers. Among the two investigated chiral selectors, vancomycin resulted to be the most useful chiral selector allowing relatively high chiral resolution of the studied compounds even at low concentration. The optimized method (10 mM sorbic acid/histidine, pH 5, and 10 mM of vancomycin) was used for the analysis of real samples such as teeth dentine and beer.

Anti-Bacterial Agents↗
PubMedDate not supplied

[Antidiabetic and anticoagulant properties of the heparin-glutamic acid complex].

Natural heparin complexes proved to activate the anticoagulation system. The obtained experimental data convincingly confirm that glutamic acid alone, and particularly in a complex with heparin, has a considerable preventive potential and efficiently protects experimental animals with induced diabetes mellitus.

Alloxan↗
PubMed2001

Differential regulation of forebrain glutamic acid decarboxylase mRNA expression by aging and stress.

In aging brain, degeneration or functional impairment of the hippocampus has been connected with stress dysregulation, serving to disinhibit stress responses and allow for glucocorticoid hypersecretion and its attendant pathophysiology. Hippocampal dysfunction appears to be communicated to paraventricular hypothalamic corticotropin-releasing hormone neurons by way of subcortical GABAergic neurons. As such, hippocampal-hypothalamic relays are likely to play an important role in age-related stress dysfunction. To test this hypothesis, regulation of glutamic acid decarboxylase isoform mRNA was studied in young (3 months), middle aged (15 months) and aged (30 months) Fischer 344/Brown Norway F1 hybrid rats. Basal expression of glutamic acid decarboxylase (GAD) 65 mRNA was increased in the medial preoptic area and posteromedial bed nucleus of the stria terminalis (BST) in aged rats relative to both middle-aged and young groups. Unlike young or middle-aged animals, exposure to chronic intermittent stress decreased GAD65 mRNA levels in the medial preoptic area and posteromedial BST of aged rats. Thus, while aged rats show evidence of elevated basal GABA synthesis, chronic stress causes differential loss of GAD in hippocampal-PVN relays, consistent with reduced PVN inhibition.

Aging↗
PubMed2003

Enantioselective chromenone benzoxazole receptor for glutamic acid and its derivatives.

Combination of a binaphthyl unit with chromenone benzoxazole fragments provided a chiral receptor that is enantioselective for glutamic acid and its derivatives. The receptor racemic mixture was resolved by TLCs impregnated with (R,R)-thiodilactic acid. High association constants were measured for dansylglutamic acid, using a fluorescent method. This receptor can be used for the resolution of the tosylglutamic acid racemic mixture.

Benzoxazoles↗
PubMed1970

Product inhibition of the fermentative formation of glutamic acid.

The addition of penicillin to cells of Corynebacterium glutamicum growing in 5-liter fermentors initiated the excretion of glutamic acid. The rate of glutamate production in fermentors declined continuously with time and reached 75% of the initial rate in 24 hr after penicillin had been added. The addition of glutamate to resting cell suspensions had only a slight effect on sugar utilization but caused a marked decrease in glutamate excretion. It is suggested that the high level of glutamate accumulating in the fermentation broth is responsible for inhibiting its own production.

Corynebacterium↗
PubMed2002

Novel 1-hydroxyazole bioisosteres of glutamic acid. Synthesis, protolytic properties, and pharmacology.

A number of 1-hydroxyazole derivatives were synthesized as bioisosteres of (S)-glutamic acid (Glu) and as analogues of the AMPA receptor agonist (R,S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA, 3b). All compounds were subjected to in vitro pharmacological studies, including a series of Glu receptor binding assays, uptake studies on native as well as cloned Glu uptake systems, and the electrophysiological rat cortical slice model. Compounds 7a,b, analogues of AMPA bearing a 1-hydroxy-5-pyrazolyl moiety as the distal carboxylic functionality, showed only moderate affinity for [3H]AMPA receptor binding sites (IC(50) = 2.7 +/- 0.4 microM and IC(50) = 2.6 +/- 0.6 microM, respectively), correlating with electrophysiological data from the rat cortical wedge model (EC(50) = 280 +/- 48 microM and EC(50) = 586 +/- 41 microM, respectively). 1-Hydroxy-1,2,3-triazol-5-yl analogues of AMPA, compounds 8a,b, showed high affinity for [3H]AMPA receptor binding sites (IC(50) = 0.15 +/- 0.03 microM and IC(50) = 0.13 +/- 0.02 microM, respectively). Electrophysiological data showed that compound 8a was devoid of activity in the rat cortical wedge model (EC(50) > 1000 microM), whereas the corresponding 4-methyl analogue 8b was a potent AMPA receptor agonist (EC(50) = 15 +/- 2 microM). In accordance with this disparity, compound 8a was found to inhibit synaptosomal [3H]D-aspartic acid uptake (IC(50) = 93 +/- 25 microM), as well as excitatory amino acid transporters (EAATs) EAAT1 (IC(50) = 100 +/- 30 microM) and EAAT2 (IC(50) = 300 +/- 80 microM). By contrast, compound 8b showed no appreciable affinity for Glu uptake sites, neither synaptosomal nor cloned. Compounds 9a-c and 10a,b, possessing 1-hydroxyimidazole as the terminal acidic function, were devoid of activity in all of the systems tested. Protolytic properties of compounds 7a,b, 8b, and 9b were determined by titration, and a correlation between the pK(a) values and the activity at AMPA receptors was apparent. Optimized structures of all the synthesized ligands were fitted to the known crystal structure of an AMPA-GluR2 construct. Where substantial reduction or abolition of affinity at AMPA receptors was observed, this could be rationalized on the basis of the ability of the ligand to fit the construct. The results presented in this article point to the utility of 1-hydroxypyrazole and 1,2,3-hydroxytriazole as bioisosteres of carboxylic acids at Glu receptors and transporters. None of the compounds showed significant activity at metabotropic Glu receptors.

Animals↗