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At least 145 records · Page 8Linked to original sources
PubMed1978

The absorption by human volunteers of glutamic acid from monosodium glutamate and from a partial enzymic hydrolysate of casein.

Peripheral plasma concentrations of glutamic and aspartic acids and alanine were measured after ingestion of monosodium glutamate or a pancreatic hydrolysate of casein by human volunteers. The doses of each material were such that they contained similar amounts of glutamic acid. Plasma glutamic acid concentrations rose promptly after the monosodium glutamate but mean peak concentrations were well below those likely to cause neurological damage. Plasma aspartic acid concentrations also rose after the monosodium glutamate but the behaviour of plasma alanine concentrations suggested that intestinal transamination of glutamic acid was insufficient to cause an appreciable rise in alanine concentration in the peripheral plasma. Significant increments in plasma glutamic acid concentrations did not occur after the pancreatic hydrolysate of casein and it is probable that competition for absorptive mechanisms by other amino acids, both free and peptide-bound, causes absorption of glutamic acid to be slower from mixtures of peptides and amino acids than from monosodium glutamate itself.

Absorption↗
PubMed1996

Levels of glutamic acid decarboxylase (GAD), gamma amino butyric acid transaminase (GABA-T), glutamic acid dehydrogenase (GLDH) and proteins in cerebrospinal fluid of certain neurological disorders.

Important glutamic acid metabolising enzymes in brain namely GAD, GABA-A and GLDH have been studied in the CSF of tuberculous meningitis (TBM), pyogenic meningitis (PM) and brain tumor (BT). The levels of GAD were reported as picomoles of GABA formed/mg of protein/hour. The control levels of the enzymes were GAD = 129 +/- 54, GABA-T = 533 +/- 146 and GLDH...O. 198 +/- 0.097. The levels of GAD were significantly increased (P < 0.001), in both TBM and PM, the values were 302 +/- 81 and, 290 +/- 97 respectively. The GABA-T levels were significantly raised (P < 0.001) only in PM cases 639 +/- 171. The values were reported as nano moles of GABA transformed/mg of protein/hour. The CSF-GLDH levels (unit/litre) showed significant elevation (P +/- 0.001) in TBM in PM, the values were 0.41 +/- 0.1 and 0.41 +/- 0.18 respectively. The CSF proteins were markedly elevated in all the conditions.

4-Aminobutyrate Transaminase↗
PubMed1987

Immunocytochemical localization of glutamic acid decarboxylase (GAD) and glutamine synthetase (GS) in the area postrema of the cat. Light and electron microscopy.

The present study was designed to investigate the existence of two key enzymes involved in the metabolism of gamma-aminobutyric acid, glutamic acid decarboxylase (GAD) and glutamine synthetase (GS), in the area postrema (AP) of the cat. The results showed that punctuate structures of variable size corresponding to axon terminals, exhibited GAD-immunoreactivity and were distributed in varying densities. The greatest accumulation was present in the caudal and middle segment of the AP and particularly in the area subpostrema, where the aggregation of terminals was extremely dense. The population of the GAD-labelled axon profiles gradually decreased toward the solitary complex. No neuronal bodies were labelled in our preparations. The electron microscopic studies revealed a large variety of contacts between labelled terminals and unlabelled dendrites, axons or neurons. The possibility that the GAD-immunoreactive terminals might correspond to vagal afferent projections was discussed on the basis of our observations and of other studies that employed horseradish peroxidase or degeneration methods. GS-immunoreactivity was seen in ependymoglial cells of the AP, particularly toward the caudal region, and in astrocytes and their processes of the AP proper. The latter were frequently observed around capillaries. The presence of both GAD-immunoreactive profiles and GS-immunostained ependymoglial cells and astrocytes in the AP, provided further immunocytochemical evidence of the functional correlation between the two enzymes.

Animals↗
PubMed1982

[Total parenteral nutrition of premature infants: metabolic effects of an exogenous supply of L-aspartic acid and L-glutamic acid].

Within the scope of clinically indicated total parenteral nutrition of premature infants, a comparative randomized study was performed to examine--by means of nitrogen-balance studies and determination of the free amino acids in the serum--the metabolic effects of absent or parallel intake of 1.140 mumol L-aspartic acid plus 2.160 mumol L-glutamic acid per kg body weight per day in complete L-amino acid solutions with a comparative E/T-ratio and with identical intake of all other nutrients adapted to the requirement. 1. The nitrogen balance level was not affected by the absent or parallel intake of the dicarbonic acids. 2. Intravenous intakes of glycine plus L-serine, which are higher than 2.5 mmol per kg body weight and day, caused statistically significant increased serum concentrations of glycine and L-serine. Such intakes are obviously above the physiologic regulation range. 3. The absent intake of L-aspartic acid and L-glutamic acid resulted in parallel, statistically significant reduced serum concentrations of aspartic acid and asparagine as well as in homeostatic serum concentrations of glutamic acid and glutamine. Despite the only 15-20% higher intake of proline, alanine and arginine under the infusion regimen lacking dicarbonic acids, there was a parallel, statistically significant marked increase in the serum concentrations of proline, alanine, arginine and methionine as well as a statistically significant marked decrease in those of taurine. Under the infusion regimen containing dicarbonic acids exclusively, constant homeostatic serum concentrations of these amino acids as well as of aspartic acid and glutamic acid were measured. 4. A direct or indirect effect of the exogenous supply of L-aspartic acid and/or L-glutamic acid on the homeostasis of aspartic acid and asparagine, on the endogenous turnover of L-alanine and L-proline as well as on the physiologic course of the Krebs-Henseleit cycle and of the "transsulfuration pathway" must be discussed. 5. Since the supply rates of L-aspartic acid plus L-glutamic acid chosen in series 2 (when continuously administered during 24-hour periods) apparently do not cause any disturbance in amino-acid homeostasis, it is established that under the nutritional conditions given this intake lies within the respective physiologic regulation range and therefore is atoxic.

Amino Acids↗
PubMed1990

Probing the role of glutamic acid 144 in the EcoRI endonuclease using aspartic acid and glutamine replacements.

The x-ray structure of the EcoRI endonuclease-DNA complex (3) suggests that hydrogen bonds between amino acids, glutamic acid 144, arginine 145, and arginine 200, and major groove base moieties are the molecular determinants of specificity. We have investigated residue 144 using aspartate and glutamine substitutions introduced by site-directed mutagenesis. Substitution with glutamine results in a null phenotype (at least a 2000-fold reduction in activity). On the other hand, the aspartic acid mutant (ED144) retained in vivo activity. Substrate binding and catalytic studies were done with purified ED144 enzyme. The affinity of the ED144 enzyme for the canonical sequence 5'-GAATTC-3' is about 340-fold less than the wild-type (WT) enzyme, while its affinity for nonspecific DNA is about 50 times greater. The ED144 enzyme cleaves one strand in the EcoRI site in plasmid pBR322 with a kcat/Km similar to WT. In contrast to the WT enzyme, the ED144 enzyme dissociates after the first strand cleavage. Partitioning between cleavage and dissociation at the first and second cleavage steps for the ED144 enzyme is extremely salt-sensitive. The altered partitioning results largely from a destabilization of the enzyme-DNA complex, particularly the enzyme-nicked DNA complex, with only small changes in the respective cleavage rates. The hydrogen bonds of Glu-144 are critical, they appear to act cooperatively with other specificity contacts to stabilize the enzyme-DNA complex.

Base Sequence↗
PubMed1997

Phosphorylation of serine residues 3, 6, 10, and 13 distinguishes membrane anchored from soluble glutamic acid decarboxylase 65 and is restricted to glutamic acid decarboxylase 65alpha.

GAD65, the smaller isoform of the gamma-aminobutyric acid-synthesizing enzyme glutamic acid decarboxylase is detected as an alpha/beta doublet of distinct mobility on SDS-polyacrylamide gel electrophoresis. Glutamic acid decarboxylase (GAD) 65 is reversibly anchored to the membrane of synaptic vesicles in neurons and synaptic-like microvesicles in pancreatic beta-cells. Here we demonstrate that GAD65alpha but not beta is phosphorylated in vivo and in vitro in several cell types. Phosphorylation is not the cause of the alpha/beta heterogeneity but represents a unique post-translational modification of GAD65alpha. Two-dimensional protein analyses identified five phosphorylated species of three different charges, which are likely to represent mono-, di-, and triphosphorylated GAD65alpha in different combinations of phosphorylated serines. Phosphorylation of GAD65alpha was located at serine residues 3, 6, 10, and 13, shown to be mediated by a membrane bound kinase, and distinguish the membrane anchored, and soluble forms of the enzyme. Phosphorylation status does not affect membrane anchoring of GAD65, nor its Km or Vmax for glutamate. The results are consistent with a model in which GAD65alpha and -beta constitute the two subunits of the native GAD65 dimer, only one of which, alpha, undergoes phosphorylation following membrane anchoring, perhaps to regulate specific aspects of GAD65 function in the synaptic vesicle membrane.

Amino Acid Sequence↗
PubMed1972

Effect of L-aspartic acid and L-glutamic acid on production of L-proline.

To elucidate the effect of aspartic acid on growth of Kurthia catenaforma during the proline fermentation, this organism was compared with other bacteria with respect to the rate of consumption of aspartic acid, and to the activities of enzymes concerned in the metabolism of aspartic acid. Although no marked difference in enzyme activities was observed, the aspartic acid consumption rate of K. catenaforma was markedly higher than that of other organisms. The consumption of glutamic acid by K. catenaforma was not detected at 24 hr of culture. The difference between the consumption of aspartic acid and glutamic acid in this strain might result from a difference in permeability to the amino acids. We considered that L-glutamic acid might substitute for L-aspartic acid if the uptake of glutamic acid could be increased. A number of detergents were screened for their effect on consumption of glutamic acid. Cetyltrimethylammonium bromide, sodium laurylphosphate, and polyoxyethylene sorbitan monolaurate were found to increase the transport rate of glutamic acid, but not of aspartic acid. A method of producing L-proline from glutamic acid was established with the aid of detergents.

Aspartate Aminotransferases↗
PubMed1994

High level of concordance between assays for glutamic acid decarboxylase antibodies. The First International Glutamic Acid Decarboxylase Antibody Workshop.

Glutamic acid decarboxylase antibodies (GADAbs) are being increasingly used in clinical and research programs for the prediction and classification of insulin-dependent diabetes mellitus (IDDM). A number of different assay formats for the measurement of GADAbs have been reported, but the degree of concordance between assays is unknown. In this study, GADAbs were measured on 16 coded sera in 34 assays to examine concordance between GADAb assays and establish the feasibility of an international GADAb standard of measurement unit. The 16 lyophilized coded samples consisted of sera from healthy control subjects (n = 2), IDDM patients (n = 3), a patient with polyendocrine autoimmunity (n = 1), and duplicate dilutions of plasmapheresis serum from a patient with stiff-man syndrome (SMS). A high level of concordance was found in the ranking of GADAb levels (P = 0.99, Friedman's test) in the samples. Thirteen (38%) assays could reproducibly distinguish dilutions of SMS serum and detect GADAbs in all IDDM and polyendocrine autoimmunity sera tested. Although assessed on only four samples, disease specificity was 100% in 29 assays. The majority of assays that immunoprecipitated radiolabeled GAD gave high results for sensitivity and specificity. Enzyme-linked immunosorbent assays and assays using immunofluorescence were generally less sensitive. Several assays, in particular those measuring GAD enzymatic activity immunoprecipitated in fluid phase from rat brain homogenate, showed a prozone-like phenomenon in the SMS dilution curve. Interpolation of results from a standard curve into workshop units resulted in relatively low scatter in samples with lower levels of GADAbs. Hence, the use of an international reference serum to enable comparison of results between laboratories appears feasible.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Measurement of the transfer of the nitrogen moiety of intestinal lumen glutamic acid in man after oral ingestion of l-[15N]glutamic acid.

1. The measurement of the intestinal metabolism of the nitrogen moiety of glutamic acid has been investigated by oral ingestion of l-[15N]glutamic acid and sampling of arterialized blood. 2. Measurements have been made in six normal adults weighing an average of 72.8 kg ingesting 100 mg of l-[15N]glutamic acid after an overnight fast. 3. Measurement of the enrichment of arterial glutamic acid, glutamine and alanine was by gas chromatography-mass spectrometry. Isotopic enrichment of the amino acids was followed for 150 min after the ingestion of the amino acid. 4. Arterialized venous blood amino acid concentrations, measured by h.p.l.c., demonstrated no significant changes during the course of the experiment. 5. From the observed appearance of label in arterialized glutamic acid, alanine and glutamine, little luminal glutamic acid reaches the extracellular pool. The majority of the administered nitrogen label appears in the arterial alanine and glutamine components.

Administration, Oral↗
PubMed1971

Specific immune response genes of the guinea pig. I. Dominant genetic control of immune responsiveness to copolymers of L-glutamic acid and L-alanine and L-glutamic acid and L-tyrosine.

The immunogenicity of three random copolymers of amino acids with L-glutamic acid and L-alanine (GA), L-glutamic acid and L-tyrosine (GT), or L-glutamic acid, L-alanine, and L-tyrosine (GAT), administered in complete Freund's adjuvant, was studied in several inbred and random-bred guinea pig strains. The animals were tested for delayed sensitivity and their sera were assayed for the presence of antibody directed against the immunizing polymer. All of the guinea pigs developing delayed hypersensitivity also had significant antibody levels in their sera. Inbred strain 2 guinea pigs responded to immunization with GA, but failed to form detectable responses to GT. Inbred strain 13 animals, on the other hand, responded to GT, but not to GA. The (2 x 13)F(1) hybrids responded to both GA and GT with both delayed hypersensitivity and circulating antibody. Thus, the ability of these inbred guinea pigs to respond immunologically to GA or GT is controlled by distinct autosomal dominant genes. A variable percentage of random-bred guinea pigs, depending on their source as well as their strain, responded to immunization with GA and with GT. All guinea pigs, both inbred and random bred, responded to immunization with GAT. The ability to respond immunologically to GAT, therefore, does not seem to be under simple genetic control. However, the levels of anti-GAT antibody found in the sera of animals lacking the ability to respond to GA were much lower than those detected in GA responder animals.

Alanine↗
PubMed1982

N-acetyl-L-aspartic acid, N-acetyl-alpha-L-aspartyl-L-glutamic acid and beta-citryl-L-glutamic acid in human urine.

N-Acetyl-L-aspartic acid (NA-Asp), N-acetyl-alpha-L-aspartyl-L-glutamic acid (NA-Asp-Glu) and beta-citryl-L-glutamic acid (beta-CG), which are known to occur in the brain, have been isolated from human urine. Their identities were proved by comparing them with synthetic NA-Asp, NA-Asp-Glu and beta-CG using electrophoretic and chromatographic methods and by acid hydrolysis. A method was developed for the quantitation of NA-Asp, NA-Asp-Glu and beta-CG in human urine. It consists of ion-exchange chromatography followed by gas-chromatographic analysis. The amounts of urinary excretion of NA-Asp, NA-Asp-Glu and beta-CG were 41.2 +/- 10.1 (n = 27), 20.8 +/- 9.6 (n = 27) and 30.2 +/- 13.2 (n = 21) mumol/g creatinine in adult males, and 62.2 +/- 16.3 (n = 27), 24.0 +/- 8.2 (n = 27) and 40.5 +/- 21.1 (n = 24) mumol/g creatinine in adult females, respectively.

Adult↗
PubMed1995

Dopamine-glutamic acid interaction in the anterior hypothalamus: modulatory effect of melatonin.

The aim of the present study was to investigate the role of melatonin as neuromodulator. For that, the effects of melatonin on the extracellular concentrations of excitatory amino acids, glutamic and aspartic acids, were investigated in the anterior hypothalamus and parieto-temporal cortex of the conscious rat using an intracerebral perfusion system. Melatonin at doses of 250 nM and 1 microM produced no effects on extracellular glutamate and aspartate concentrations in these two areas of the brain. Since amphetamine releases dopamine we perfused melatonin into the anterior hypothalamus and parieto-temporal cortex after a previous injection of amphetamine. Interestingly, we found a release of glutamic acid (p < 0.01) and aspartic acid (p < 0.01) produced by melatonin only when the increase (157%) of the extracellular dopamine concentration evoked by amphetamine was inhibited by melatonin in the anterior hypothalamus. The possibility is discussed of melatonin exerting its effects when the dopaminergic system is activated.

Animals↗