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At least 217 records · Page 12Linked to original sources
PubMed1973

Biosynthesis of glutamic acid in Saccharomyces: accumulation of tricarboxylic acid cycle intermediates in a glutamate auxotroph.

Aconitaseless glutamic acid auxotroph MO-1-9B of Saccharomyces grew in glutamic acid-supplemented minimal medium, but failed to grow when glutamic acid was substituted by proline, arginine, ornithine, or glutamine. This mutant was also unable to utilize lactate or glycerol as a carbon source. Under a glutamic acid-limiting condition, by using acetate-1-(14)C as tracer, the mutant accumulated rather large amounts of (14)C-citric acid and (14)C-succinic acid when compared with the wild-type strain. Under excess glutamic acid supplementation, accumulation of citric acid and succinic acid was considerably reduced. When (14)C-glutamic acid-(U) was used as tracer, (14)C-alpha-ketoglutaric acid, (14)C-citric acid, and (14)C-succinic acid were accumulated in the mutant. The citric acid peak was the largest, followed by alpha-ketoglutaric acid and succinic acid. In the wild-type strain under similar conditions, only small amounts of (14)C-citric acid and (14)C-succinic acid and no (14)C-alpha-ketoglutaric acid were accumulated.

Acetates↗
PubMed2005

Molecular ordering and adsorbate induced faceting in the Ag{110}-(S)-glutamic acid system.

The adsorption of the amino acid, (S)-glutamic acid, was investigated on Ag{110} as a function of coverage and adsorption temperature using the techniques of scanning tunneling microscopy, low energy electron diffraction, and reflection absorption infrared spectroscopy. In the monolayer, (S)-glutamic acid was found to adsorb predominantly in the anionic glutamate form. Several discrete ordered adlayer structures were observed depending on preparation conditions. In addition, (S)-glutamic acid was found to induce both one- and two-dimensional faceting of the Ag{110} surface. In some cases, evidence was found that the 2-D faceting involved the creation of a chiral facet distribution. A comparison is made of the Ag/(S)-glutamic acid system with analogous studies of amino acids on Cu.

Journal Article↗
PubMed1992

Identification of aspartic acid 514 through glutamic acid 542 as a glycoprotein Ib-IX complex receptor recognition sequence in von Willebrand factor. Mechanism of modulation of von Willebrand factor by ristocetin and botrocetin.

As the first step in hemostasis, the binding of von Willebrand factor (vWF) to the platelet membrane glycoprotein (GP) Ib-IX complex is essential for platelet adhesion at high-shear blood flow. This interaction in vivo requires the prior binding of vWF to the subendothelial matrix, a process which exposes a normally cryptic binding site on vWF for the GP Ib-IX complex. This process can be mimicked in vitro by modulators such as ristocetin or the snake venom protein botrocetin or by desialation of vWF. We have previously localized the GP Ib binding site on vWF to a monomeric dispase fragment which extends from Leu-480/Val-481 to Gly-718 in the primary sequence of mature vWF [Andrews, R. K., Gorman, J. J., Booth, W. J., Corino, G. L., Castaldi, P. A., & Berndt, M. C. (1989) Biochemistry 28, 8326-8336]. This fragment also contains a distinct binding site for botrocetin. Analysis of synthetic peptides corresponding to hydrophilic stretches of sequence within this fragment indicated that the sequence Asp-514-Glu-542 represents a major adhesive sequence involved in receptor recognition. This peptide inhibited both the ristocetin- and botrocetin-mediated binding of vWF to either platelets or purified GP Ib-IX complex (IC50 approximately 50-200 microM) as well as the asialo-vWF- and bovine vWF-dependent agglutination of platelets. Both the N- and C-terminal halves of the peptide were inhibitory but less so than the intact peptide. This peptide also inhibited botrocetin binding to vWF, suggesting that botrocetin modulates vWF-GP Ib interaction by binding in close proximity to the vWF adhesion sequence.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1989

Uptake of gamma-aminobutyric acid and L-glutamic acid by synaptosomes from postmortem human cerebral cortex: multiple sites, sodium dependence and effect of tissue preparation.

The uptake of gamma-aminobutyric acid (GABA) and L-glutamic acid by synaptosomes prepared from frozen postmortem human brain was shown to be effected via distinct high and low affinity sites. At approximately 17 h postmortem delay, the kinetic parameters for GABA uptake were: high affinity site, Km 7.1 +/- 2.5 microM, Vmax 18.7 +/- 4.8 nmol.min-1 per 100 mg protein; low affinity site, Km 2 +/- 1 mM, Vmax 425 +/- 250 nmol.min-1 per 100 mg protein (means +/- S.E.M., n = 13). Kinetic parameters for L-glutamate uptake were: high affinity site, Km 7.5 +/- 1.0 microM, Vmax 85 +/- 8 nmol.min-1 per 100 mg protein; low affinity site, Km 1.8 +/- 1.2 mM. Vmax 780 +/- 175 nmol.min-1 per 100 mg protein (n = 11). A detailed kinetic analysis of high affinity GABA uptake was performed over a range of sodium ion concentrations. The results were consistent with a coupling ratio of one Na+ ion to one GABA molecule; a similar result was found with rat brain synaptosomes. However, rat and human synaptosomes differed in the degree to which the substrate affinity of the high affinity GABA uptake site varied with decreasing Na+ ion concentration. High affinity GABA uptake was markedly affected by the method used to freeze and divide the tissue, but did not vary greatly in different cortical regions. There was some decline of high affinity GABA uptake activity with postmortem delay, apparently due to a loss of sites rather than a change in site affinity.

Adult↗
PubMed1989

[Effects of noradrenaline,glycine, gamma-aminobutyric acid and L-glutamic acid on spinal field potentials in the rat].

Noradrenaline (NE), glucine (GLY), gamma-aminobutyric acid (GABA) and L-glutamic acid (L-GLU) were locally applied to the dorsal surface of lumbar spinal cord on anesthetized and immobilized rats and their effects on segmental (SP) and descending (DP) spinal field potentials were examined. Both waves N and P of SP and DP were reduced markedly in amplitudes following local application of NE. A significant decrease in amplitude of wave N and a remarkable increase in wave P in both SP and DP were shown during the application of GLY, GABA and L-GLU. The results suggest that these neurotransmitters may be involved in the generation of waves N and P, particularly affecting the activities of interneurons in the spinal dorsal horn.

Animals↗
PubMed1976

Effects of kainic acid, a cyclic analogue of glutamic acid, on cyclic nucleotide accumulation in slices of rat cerebellum.

The concentration of cyclic AMP (cAMP) and cyclic GMP (cGMP) in slices of rat cerebellum was increased markedly in the presence of 100 muM kainic acid, a cyclic analogue of glutamic acid. No acitvity was detected in other brain areas at various dosed or incubation times. Ksainic acid was significantly more potent than glutamic acid and other glutamate-like compounds. The increases in cAMP and cGMP could be differentially inhibited with theophylline or cocaine respectively, but both systems required calcium. Compounds similar in structure to kainic acid or glutamate did not block the effects of kainic acid.

Animals↗
PubMed1978

Aspinous and sparsely-spinous stellate neurons in the visual cortex of rats contain glutamic acid decarboxylase.

Glutamic acid decarboxylase (GAD), the enzyme that synthesizes the neurotransmitter gamma-amino-butyric acid (GABA), has been localized in the rat visual cortex by immunocytochemical methods with both light and electron microscopy. In both colchicine-injected and non-injected preparations of the visual cortex, GAD-positive reaction product was observed in somata, proximal dendrites and axon terminals of non-pyramidal neurons. The GAD-positive terminals were observed to form symmetric synaptic junctions most commonly with dendritic shafts and somata of pyramidal and stellate neurons and less frequently with initial axon segments of pyramidal neurons and dendritic spines. In colchicine-injected preparations, GAD-positive somata were located in all cortical layers including the immediately subjacent white matter. In contrast, sections from non-injected rats displayed GAD-positive somata within a superficial and a deep cortical band. The GAD-positive somata observed in both types of preparations received both symmetric and asymmetric synaptic junctions, lacked apical dendrites, and had radially oriented dendrites of small diameter. These characteristics of GAD-positive neurons indicate that they are aspinous and sparsely-spinous stellate neurons. The localization of GAD within these neurons in combination with physiological and pharmacological data indicate that these local circuit neurons mediate GABA-ergic inhibition in the neocortex.

Animals↗
PubMed1991

Conversion of citrate synthase into citryl-CoA lyase as a result of mutation of the active-site aspartic acid residue to glutamic acid.

The active-site aspartic acid residue, Asp-362, of Escherichia coli citrate synthase was changed by site-directed mutagenesis to Glu-362, Asn-362 or Gly-362. Only very low catalytic activity could be detected with the Asp----Asn and Asp----Gly mutations. The Asp----Glu mutation produced an enzyme that expressed about 0.8% of the overall catalytic rate, and the hydrolysis step in the reaction, monitored as citryl-CoA hydrolysis, was inhibited to a similar extent. However, the condensation reaction, measured in the reverse direction as citryl-CoA cleavage to oxaloacetate and acetyl-CoA, was not affected by the mutation, and this citryl-CoA lyase activity was the major catalytic activity of the mutant enzyme. This high condensation activity in an enzyme in which the subsequent hydrolysis step was about 98% inhibited permitted considerable exchange of the methyl protons of acetyl-CoA during catalysis by the mutant enzyme. The Km for oxaloacetate was not significantly altered in the D362E mutant enzyme, whereas the Km for acetyl-CoA was about 5 times lower. A mechanism is proposed in which Asp-362 is involved in the hydrolysis reaction of this enzyme, and not as a base in the deprotonation of acetyl-CoA as recently suggested by others. [Karpusas, Branchaud & Remington (1990) Biochemistry 29, 2213-2219; Alter, Casazza, Zhi, Nemeth, Srere & Evans, (1990) Biochemistry 29, 7557-7563].

Acetyl Coenzyme A↗