Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “GLUTAMIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1993

Cloning and expression of large isoform of glutamic acid decarboxylase from human pancreatic islet.

Glutamic acid decarboxylase (GAD) catalyzes formation of gamma-aminobutyric acid from glutamic acid and is a major autoantigen in insulin-dependent diabetes mellitus. Its two isoforms, GAD65 and GAD67, are encoded by two separate genes. We prepared human islet cDNA library and screened it with cDNA probes of rat brain GAD67. We cloned the cDNA for GAD67, the large isoform of glutamic acid decarboxylase, and determined its nucleotide sequence. Sequencing of the resulting clone identified a 1,785 residue open-reading frame encoded a 594 amino acid polypeptide that showed a 99.4% similarity with GAD67 from human brain. The bacterially expressed human islet GAD67 protein was enzymatically active and immunoreactive. The isolation of cDNA for this additional islet GAD isoforms will be important in studying the etiology and pathogenesis of IDDM.

Amino Acid Sequence↗
PubMed1975

Physical and chemical properties of the NH2-terminal glutamic acid and lysine forms of human plasminogen and their derived plasmins with an NH2-terminal lysine heavy (A) chain.

Comparative physical and chemical data are described for the human NH2-terminal Glu-plasminogen and Lys-plasminogen forms in order to determine the exact relationship between these two types of the zymogen. The molecular weights of Glu-plasminogen and Lys-plasminogen were similar and were determined to be 83, 800 plus or minus 4, 500 and 82, 400 plus or minus 3, 300, respectively, by sedimentation equilibrium methods. The molecular weights were identical in dodecyl sulfate solutions, approximately 83, 000, by sedimentation equilibrium methods. The sedimentation coefficients, s-020, w of Glu-plasminogen and Lys-plasminogen were determined to be 5.0 S, and 4.4 S, respectively. These two plasminogen forms had different partial specific volumes, and calculations of the frictional coefficients from sedimentation coefficients and molecular weights indicated conformation differences. Glu-plasminogen appeared to be larger in size than Lys-plasminogen in acrylamide gel-dodecyl sulfate electrophoresis. The amino acid compositions of Glu-plasminogen and Lys-plasminogen, and their major isolated isoelectric forms, were found to be similar, but several amino acid residues (glutamic acid, alanine, isoleucine, phenylalanine, and lysine) were found to be significantly higher in the Glu-plasminogen forms. The derived plasmins from both the Glu- and Lys-plasminogens with an nh2-terminal Lys- heavy (A) chain were found to have identical molecular weights of 76, 500 plus or minus 2, 500, and sedimentation coefficients, s-020, w of 4.3 S.

Amino Acid Sequence↗
PubMed1991

Use of high-performance liquid chromatography for assay of glutamic acid decarboxylase. Its limitation in use for post-mortem brain.

Rat brain, obtained 10 min after death, contained high levels of endogenous gamma-aminobutyric acid (GABA) and glutamic acid. Incubation of this brain homogenate at 37 degrees C indicated decrease of GABA with time due to degradation by GABA-transaminase. Reported high-performance liquid chromatographic (HPLC) methods for glutamic acid decarboxylase (GAD) assay depend on the difference between the GABA content of the reaction mixture after and before the incubation period. None of the methods considered the degradation of GABA during incubation. Furthermore, during determination of the Michaelis constant (KM) for the reaction none of them considered the endogenous substrate. Here we have focused on these factors which seriously affect the maximum velocity (Vmax) and KM values during GAD assay by the HPLC technique. By a simple and rapid HPLC technique we have measured GAD activity in post-mortem rat brain after removing endogenous glutamic acid by charcoal treatment and using gabaquline to prevent GABA degradation during incubation period. By this method a Vmax value of 46 +/- 4 nmol/h/mg protein and a KM value of 7.5 +/- 0.6 mM were observed for GAD activity of crude brain homogenate. For a comparative study, we have carried out radiometric assay of GAD activity from the same sample and observed a Vmax of 48 +/- 6 nmol/h/mg protein and KM of 6.9 +/- 0.4 mM.

Animals↗
PubMed1980

The effects of potassium and membrane potential on sodium-dependent glutamic acid uptake.

The uptake of L-glutamic acid into brush-border membrane vesicles isolated from rat renal proximal tubules is NA+-dependent. In contrast to Na+-dependent uptake of D-glucose, pre-equilibration of the vesicles with K+ stimulates L-glutamic acid uptake. Imposition of a K+ gradient ([Ki+] > [Ko+]) further enhances Na+-dependent L-glutamic acid uptake, but leaves K+-dependent glucose transport unchanged. If K+ is present only at the outside of the vesicles, transport is inhibited. Intravesicular Rb+ and, to a lesser extent, Cs+ can replace intravesicular K+ to stimulate L-glutamic acid uptake. Changes in membrane potential incurred by the imposition of an H+-diffusion potential or anion replacement markedly affect Na+-dependent glutamic acid uptake only in the presence of K+. Experiments with a potential-sensitive cyanine dye also indicate that, in the presence of intravesicular K+ a charge movement is involved in Na+-dependent transport of L-glutamic acid. The data indicate that Na+-dependent L-glutamic acid transport can be additionally energized by a K+ gradient. Furthermore, intravesicular K+ render Na+-dependent L-glutamic acid transport sensitive to changes in the transmembrane electrical potential difference.

Animals↗
PubMed1992

Clozapine and haloperidol have differential effects on glutamic acid decarboxylase mRNA in the pallidal nuclei of the rat.

The striatum, and one of its targets, the pallidum (globus pallidus and entopeduncular nucleus) are based ganglia nuclei involved in extrapyramidal movement control. Gamma-aminobutyric acid (GABA)ergic neurons of the pallidum may be important for the expression of the effects of agents which alter striatal neurotransmission. In this study, rats were treated once daily for 28 days with either haloperidol or clozapine, two drugs which respectively, do and do not, induce extrapyramidal movement disorders. In situ hybridization histochemistry was used to quantify the levels of labeling for the messenger ribonucleic acid encoding glutamic acid decarboxylase, the main synthesizing enzyme for GABA in neurons of the striatum, globus pallidus, and entopeduncular nucleus. Neither drug treatment altered levels of labeling in the striatum. Haloperidol treatment increased the level of labeling in the entopeduncular nucleus and clozapine treatment increased labeling in the globus pallidus suggesting that these drugs exert different regulatory effects on pallidal neurons.

Animals↗
PubMed1991

Modification of gastric pH with oral glutamic acid hydrochloride.

The extent to which oral glutamic acid hydrochloride decreases mean gastric pH in fasting persons with and without simulated hypochlorhydria was studied. Healthy nonsmoking men were randomly assigned to one of two drug regimens followed by the other regimen after a one-week washout period. In regimen 1 the fasting subjects received two 680-mg doses of glutamic acid hydrochloride given 10 minutes apart. Regimen 2 was the same, except that an oral dose of ranitidine 300 mg (as the hydrochloride salt) was administered one to two hours before the first dose of glutamic acid hydrochloride to simulate hypochlorhydria. Gastric pH was monitored radiotelemetrically before and after glutamic acid hydrochloride administration by using the Heidelberg capsule technique. Six men 20 to 28 years of age participated in the study. For regimen 1, the gastric pH before glutamic acid hydrochloride was given was not significantly different from that after administration (grand medians, 1.4 and 1.3, respectively). In regimen 2, the median gastric pH increased to greater than 4.0 within two hours after ranitidine treatment. Median gastric pH after the second dose of glutamic acid hydrochloride was significantly lower than before the first dose (grand medians, 1.6 and 6.2, respectively). The time to minimum pH was 2 to 15 minutes, and pH remained less than 3.0 for a mean of 45 minutes. Glutamic acid hydrochloride alone did not decrease fasting gastric pH, but it significantly reduced pH in subjects with simulated hypochlorhydria produced by orally administered ranitidine.

Acid-Base Equilibrium↗
PubMed1984

Inhibitors of crayfish glutamic acid decarboxylase.

Crayfish glutamic acid decarboxylase (GAD), like the homologous enzymes from other species, is inhibited by carbonyl-trapping agents (e.g. aminooxyacetic acid; AOAA) and sulfhydryl reagents (e.g. 5,5'-dithiobis-(2-nitrobenzoic acid); DTNB). It also is inhibited by the product GABA, many anions (e.g. SCN- and Cl-), and some cations (e.g. Zn+2). The inhibition by AOAA, but not that by DTNB, was prevented by increasing the concentration of the pyridoxal phosphate (PLP) coenzyme. GABA blocked the effects of PLP on enzyme activity. The inhibition by AOAA, DTNB, GABA, and chloride all were competitive with substrate. The effect of GABA occurs at physiological concentrations and may contribute to the regulation of GAD activity in vivo. The quantitative effect of anions is dependent on the cation with which they are administered. ATP stimulated GAD activity in homogenates prepared with potassium phosphate or Tris-acetate buffer, even when no exogenous PLP was provided.

Adenosine Triphosphate↗
PubMed1981

Impairment of instrumental learning in rats by glutamic acid diethyl ester.

Glutamic acid diethyl ester (GDEE), a putative antagonist of glutamate-induced neuronal excitations, was administered prior to an instrumental conditioning task motivated by food reinforcement. A profound impairment of learning was produced in animals receiving 240 or 480 mg/kg of GDEE. Performance was not impaired by GDEE in rats that had previously learned the task. These findings support suggestions that central excitatory processes play an important role in learning phenomena, in particular when these learning phenomena involve acquisition of new behavioral patterns.

Animals↗
PubMed1990

Synthesis of beta- and gamma-fluorenylmethyl esters of respectively N alpha-Boc-L-aspartic acid and N alpha-Boc-L-glutamic acid.

The orthogonal synthesis of N alpha-Boc-L-aspartic acid-gamma-fluorenylmethyl ester and N alpha-Boc-L-glutamic acid-delta-fluorenylmethyl ester is reported. This is a four-step synthesis that relies on the selective esterification of the side-chain carboxyl groups on N alpha-CBZ-L-aspartic acid and N alpha-CBZ-L-glutamic acid. Such selectivity is accomplished by initially protecting the alpha-carboxyl group through the formation of the corresponding 5-oxo-4-oxazolidinone ring. Following side-chain esterification, the alpha-carboxyl and alpha-amino groups are deprotected with acidolysis. Finally, the alpha-amino group is reprotected with the t-butyl-oxycarbonyl (Boc) group. Thus aspartic acid and glutamic acid have their side-chain carboxyl groups protected with the base-labile fluorenylmethyl ester (OFm) and their alpha-amino groups protected with the acid-labile Boc group. These residues, when used in conjunction with N alpha-Boc-N epsilon-Fmoc-L-lysine, are important in the formation of side-chain to side-chain cyclizations, via an amide bridge, during solid-phase peptide synthesis.

Aspartic Acid↗