Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of isocitrate dehydrogenase (NAD), isocitrate dehydrogenase (NADP) and oxoglutarate dehydrogenase have been investigated in Saccharomyces cerevisiae grown in a variety of aerobic and hypoxic conditions, the latter including oxygen deprivation, high glucose concentration, addition of inhibitors of mitochondrial protein synthesis, respiratory inhibition by azide, and impaired respiration mutants. All hypoxic conditions led to a marked decrease of oxoglutarate dehydrogenase and significant decreases of the two isocitrate dehydrogenases. According to its kinetic properties, the NAD-isocitrate dehydrogenase will not be operative in hypoxia "in vivo". From these and other related facts it is concluded that hypoxic conditions in yeast generally lead to a splitting of the tricarboxylic acid cycle and that glutamate synthesis in these conditions takes place through the coupling of the NADP-linked isocitrate and glutamate dehydrogenases.
Mol Cell Biochem 1975 Feb 28
PMID:Isocitrate dehydrogenases and oxoglutarate dehydrogenase activities of baker's yeast grown in a variety of hypoxic conditions. 109 51

Glutamate induced postsynaptic currents (g-EPSCs) were elicited by 2-5 ms glutamate pulses applied iontophoretically through high resistance (80-200 M Omega) micropipettes. Such g-EPSCs decayed with time constants in the range of 5 ms. The dose-response curves for the action of glutamate were S-shaped with a limiting log log slope of 4-6, the half maximum response concentration of glutamate was about 10(-4) Mol/l and the maximum synaptic current in the range of 30 nA. In pairs of small g-EPSCs following each other with delays between 3 and 100 ms, the second one was potentiated. For short delays potentiation was up to 60 fold. The time course of the g-EPSCs and of their potentiation can be described quantitatively with the following assumptions: 1. The simultaneous reaction of 4-6 glutamate molecules with a receptor triggers postsynaptic current flow. 2. The synaptic glutamate concentration is determined by diffusion from a point source. 3. Potentiation is due to summation of the synaptic glutamate concentrations generated by pulse 1 and by pulse 2. The relevance of these results for the interpretation of the natural EPSC is discussed.
 ...
PMID:Kinetics of postsynaptic action of glutamate pulses applied iontophoretically through high resistance micropipettes. 117 48

Palmitylcarnitine oxidation by isolated liver mitochondria has been used to investigate the interaction of fatty acid oxidation with malate, glutamate, succinate, and the malate-aspartate shuttle. Mitochondria preincubated with fluorocitrate were added to a medium containing 2mM ATP and ATPase. This system, characterized by a high energy change, allowed titration of respiration to any desired rate between States 4 and 3 (Chance, B., and Williams, G. R. (1956) Adv. Enzymol. Relat. Areas Mol. Biol. 17, 65-134). When respiration (reference, with palmitylcarnitine and malate as substrates) was set at 75% of State 3, the oxidation of palmitylcarnitine was limited by acetoacetate formation. The addition of malate or glutamate approximately doubled the rate of beta oxidation. Malate circumvented this limitation by citrate formation, but the effect of glutamate apparently was due to enhancement of the capacity for ketogenesis. The rate of beta oxidation was curtailed when malate and glutamate were both present. This curtailment was more pronounced when the malate-aspartate shuttle was fully reconstituted. Among the oxidizable substrates examined, succinate was most effective in inhibiting palmitylcarnitine oxidation. Mitochondrial NADH/NAD+ ratios were correlated positively with suppression of beta oxidation. The degree of suppression of beta oxidation by the malate-aspartate shuttle (NADH oxidation) or by succinate oxidation was dependent on the respiratory state. Both substrates extensively reduced mitochondrial NAD+ and markedly suppressed beta oxidation as respiration approached State 4. Calculations of the rates of flux of hydrogen equivalents through beta oxidation show that the suppression of beta oxidation by glutamate or by the malate-aspartate shuttle is accounted for by increased flux of reducing equivalents through mitochondrial malic dehydrogenase. This increased Flux is accompanied by an increase in the steady state NADH/NAD+ ratio and a marked decrease in the synthesis of citrate. The alpha-glycerophosphate shuttle was reconstituted with mitochondria isolated from rats treated with L-thyroxine. This shuttle was about equal to the reconstructed malate-aspartate shuttle in supression of palmitylcarnitine oxidation. This interaction could not be demonstrated in euthyroid animals owing to the low activity of the mitochondrial alpha-glycerol phosphate dehydrogenase. It is concluded that beta oxidation can be regulated by the NADH/NAD+ ratio. The observed stimulation of flux through malate dehydrogenase both by glutamate and by the malate-aspartate shuttle results in an increased steady state NADH/NAD+ ratio, and is linked to a stoichiometric outward transport of aspartate. We suggest, therefore, that some of the reducing pressure exerted by the malate-aspartate shuttle and by glutamate plus malate is provided through the energy-linked, electrogenic transport of aspartate out of the mitochondria. These results are discussed with respect to the mechanism of the genesis of ethanol-induced fatty liver.
 ...
PMID:Suppression of the mitochondrial oxidation of (-)-palmitylcarnitine by the malate-aspartate and alpha-glycerophosphate shuttles. 124 72

Cytoplasmic aspartate aminotransferase from beef kidney loses 25% of its activity on nitration with tetranitromethane while the apoenzyme about 95%. In the holoenzyme 0.5 tyrosine residue and 1.0 tyrosine residue in the apoenzyme are nitrated per enzyme protomer. In addition 1 cysteine residue per protomer is oxidized in both. The presence of substrates, alpha-ketoglutarate and glutamate, both at ten times their Km values, does not change these results. Mercaptoethanol does not affect the residual activity of either the nitrated holo or apoenzyme. Dithionite abolishes the activity of the nitrated holoenzyme by reducing tha coenzyme moiety. It has no effect on the native holoenzyme or on either the native or nitroapoenzyme.
Mol Cell Biochem 1976 Apr 28
PMID:Role of tyrosine residues in cytoplasmic aspartate aminotransferase from beef kidney. 127 58

Membrane currents were recorded from Xenopus laevis oocytes injected with C. elegans poly(A)+ RNA. In such oocytes glutamate activated an inward membrane current that desensitized in the continued presence of glutamate. Glutamate-receptor agonists quisqualate, kainate, and N-methyl-D-aspartate were inactive. The reversal potential of the glutamate-sensitive current was -22 mV, and exhibited a strong dependence on external chloride with a 48 mV change for a 10-fold change in chloride. The chloride channel blockers flufenamate and picrotoxin inhibited the glutamate-sensitive current. Ibotenate, a structural analog of glutamate, also activated a picrotoxin-sensitive chloride current. Ibotenate was inactive when current was partially desensitized with glutamate, and the responses to low concentrations of glutamate and ibotenate were additive. The anthelmintic/insecticide compound avermectin directly activated the glutamate-sensitive current. In addition, avermectin increased the response to submaximal concentrations of glutamate, shifted the glutamate concentration-response curve to lower concentrations, and slowed the desensitization of glutamate-sensitive current. We propose that the glutamate-sensitive chloride current and the avermectin-sensitive chloride current are mediated via the same channel.
Brain Res Mol Brain Res 1992 Oct
PMID:Expression of a glutamate-activated chloride current in Xenopus oocytes injected with Caenorhabditis elegans RNA: evidence for modulation by avermectin. 127 55

The pharmacological properties of two glutamate receptor subtypes, GluR-A/B and GluR-B/D, were examined in RNA-injected Xenopus oocytes using two-electrode voltage clamp. Concentration-response relations revealed that the potencies of L-glutamate, kainate, and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) varied slightly between the two receptor subtypes, but the rank order of agonist potency did not. The EC50 values for GluR-A/B receptors were 3.31 microM for AMPA, 6.16 microM for glutamate, and 57.5 microM for kainate, whereas the EC50 values for GluR-B/D receptors were 5.01 microM, 32.3 microM, and 64.6 microM for AMPA, L-glutamate, and kainate, respectively. The potencies of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX) were quantified by Schild analysis. The potency of NBQX at blocking currents mediated by GluR-A/B receptors changed depending on the agonist used to activate the receptors (pA2 values were as follows: for block of kainate, 7.23 +/- 0.01; L-glutamate, 6.78 +/- 0.02; AMPA, 6.95 +/- 0.02). Differences between agonists were less marked in cells expressing GluR-B/D receptors (pA2 values: kainate, 7.28 +/- 0.01; L-glutamate, 7.30 +/- 0.02; AMPA, 7.35 +/- 0.01). In each case, the slope of the Schild regression was not different from unity, consistent with competitive antagonism of these receptors by NBQX. CNQX also blocked GluR-A/B and GluR-B/D receptors competitively but was less potent than NBQX and did not differentiate between agonists or subunit combination. These data suggest that L-glutamate, kainate, and AMPA bind to different receptor substructures on recombinant AMPA receptors and that NBQX but not CNQX binds to these sites with different affinities. Moreover, because the properties of these binding sites vary between GluR-A/B and GluR-B/D receptors, our findings provide a basis for mutational analysis aimed at identifying receptor domains involved in agonist and antagonist binding.
Mol Pharmacol 1992 Nov
PMID:Complex pharmacological properties of recombinant alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor subtypes. 127 77

GluR1 and GluR2 cDNAs encoding non-NMDA subtypes of glutamate receptor were isolated from a rat brain cDNA library by Boulter et al. (Science, 249 (1990) 1033-1037). Functional receptors activated by kainate, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and glutamate were expressed in Xenopus oocytes injected with GluR1, GluR2 or a mixture of GluR1 and GluR2 RNAs. In GluR1-expressed oocytes, 1 mM aniracetam potentiated AMPA-induced currents by 99 +/- 10% (mean +/- S.E.M., n = 5) and glutamate-induced currents by 140 +/- 8% (n = 4), but little affected kainate-induced currents. Aniracetam was effective from a concentration of 0.1 mM, and it exhibited more conspicuous effects with the increase of the dose. In oocytes injected with GluR1 plus GluR2 RNAs, aniracetam more markedly potentiated current responses to AMPA and glutamate than those in oocytes injected with GluR1 RNA alone. For example, 1 mM aniracetam potentiated AMPA-induced currents by 396 +/- 76% (n = 4) and glutamate-induced currents by 970 +/- 65% (n = 5) in oocytes injected with 10% GluR1 and 90% GluR2 RNAs. In these oocytes, however, the potentiation of kainate-induced currents by 1 mM aniracetam was only 8 +/- 5% (n = 4). Thus, we conclude that the potentiation of the AMPA/kainate receptor by aniracetam depends on both species of agonists and subunit composition of the receptor.
Brain Res Mol Brain Res 1992 Nov
PMID:Agonist- and subunit-dependent potentiation of glutamate receptors by a nootropic drug aniracetam. 128 Dec 52

Intracellular calcium levels are stringently regulated in all cells. The nature of this regulation is incompletely understood, but recent evidence indicates that the endoplasmic reticulum plays an important role in sequestering intracellular calcium. Using methods for isolating both calsequestrin and calreticulin, we have isolated a 58 kDa, high capacity calcium binding protein that exists in microsomes that shift their density in an oxalate-mediated density shift assay. This protein which we call CBP-58 bears similarities to the endoplasmic reticulum protein, calreticulin, in that it has a pI of 4.7 containing approximately 30% glutamate and aspartate, has a high capacity for calcium, and stains blue with the carbocyanine dye, 'Stains-all'. Peptide, amino acid, nucleotide and immunochemical analyses reveal further similarities between CBP-58 and calreticulin, but also some marked differences. Its tissue distribution suggests it is highly enriched in brain versus other tissues. We believe that CBP-58 is a calreticulin-like protein and that differences in the amino acid composition and sequences may reflect species diversity in calreticulin.
Brain Res Mol Brain Res 1992 Jan
PMID:Isolation of a calreticulin-like calcium binding protein from bovine brain. 131 7

Our comparison of deduced amino acid sequences for retroviral/retrotransposon integrase (IN) proteins of several organisms, including Drosophila melanogaster and Schizosaccharomyces pombe, reveals strong conservation of a constellation of amino acids characterized by two invariant aspartate (D) residues and a glutamate (E) residue, which we refer to as the D,D(35)E region. The same constellation is found in the transposases of a number of bacterial insertion sequences. The conservation of this region suggests that the component residues are involved in DNA recognition, cutting, and joining, since these properties are shared among these proteins of divergent origin. We introduced amino acid substitutions in invariant residues and selected conserved and nonconserved residues throughout the D,D(35)E region of Rous sarcoma virus IN and in human immunodeficiency virus IN and assessed their effect upon the activities of the purified, mutant proteins in vitro. Changes of the invariant and conserved residues typically produce similar impairment of both viral long terminal repeat (LTR) oligonucleotide cleavage referred to as the processing reaction and the subsequent joining of the processed LTR-based oligonucleotides to DNA targets. The severity of the defects depended upon the site and the nature of the amino acid substitution(s). All substitutions of the invariant acidic D and E residues in both Rous sarcoma virus and human immunodeficiency virus IN dramatically reduced LTR oligonucleotide processing and joining to a few percent or less of wild type, suggesting that they are essential components of the active site for both reactions.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biol 1992 May
PMID:Residues critical for retroviral integrative recombination in a region that is highly conserved among retroviral/retrotransposon integrases and bacterial insertion sequence transposases. 131 54

The three-dimensional structure of the enzyme myeloperoxidase has been determined by X-ray crystallography to 3 A resolution. Two heavy atom derivatives were used to phase an initial multiple isomorphous replacement map that was subsequently improved by solvent flattening and non-crystallographic symmetry averaging. Crystallographic refinement gave a final model with an R-factor of 0.257. The root-mean-square deviations from ideality for bond lengths and angles were 0.011 A and 3.8 degrees. Two, apparently identical, halves of the molecule are related by local dyad and covalently linked by a single disulfide bridge. Each half-molecule consists of two polypeptide chains of 108 and 466 amino acid residues, a heme prosthetic group, a bound calcium ion and at least three sites of asparagine-linked glycosylation. There are six additional intra-chain disulfide bonds, five in the large polypeptide and one in the small. A central core region that includes the heme binding site is composed of five alpha-helices. Regions of the larger polypeptide surrounding this core are organized into locally folded domains in which the secondary structure is predominantly alpha-helical with very little organized beta-sheet. A proximal ligand to the heme iron atom has been identified as histidine 336, which is in turn hydrogen-bonded to asparagine 421. On the distal side of the heme, histidine 95 and arginine 239 are likely to participate directly in the catalytic mechanism, in a manner analogous to the distal histidine and arginine of the non-homologous enzyme cytochrome c peroxidase. The site of the covalent linkage to the heme has been tentatively identified as glutamate 242, although the chemical nature of the link remains uncertain. The calcium binding site has been located in a loop comprising residues 168 to 174 together with aspartate 96. Myeloperoxidase is a member of a family of homologous mammalian peroxidases that includes thyroid peroxidase, eosinophil peroxidase and lactoperoxidase. The heme environment, defined by our model for myeloperoxidase, appears to be highly conserved in these four mammalian peroxidases. Furthermore, the conservation of all 12 cysteine residues involved in the six intra-chain disulfide bonds and the calcium binding loop suggests that the three-dimensional structures of members of this gene family are likely to be quite similar.
J Mol Biol 1992 Jul 05
PMID:X-ray crystal structure of canine myeloperoxidase at 3 A resolution. 132 Jan 28


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>