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)

A study was undertaken to assess the role of a physiological concentration of glutamine in AS-30D cell metabolism. Flux of 14C-glutamine to 14CO2 and of 14C-acetate to glutamate was detected indicating reversible flux between glutamate and TCA cycle alpha-ketoglutarate. These fluxes were transaminase dependent. A flux analysis was compared using data from three tracers that label alpha-ketoglutarate carbon 5, [2-14C]glucose, [1-14C]acetate and [5-14C]glutamine. The analysis indicated that the probability of flux of TCA cycle alpha-ketoglutarate to glutamate was, at minimum, only slightly less than the probability of flux of alpha-ketoglutarate through alpha-ketoglutarate dehydrogenase. The apparent Km for oxidative flux of [14C]glutamine to 14CO2, 0.07 mM, indicated that this flux was at a maximal rate at physiological, 0.75 mM, glutamine. Although oxidative flux through alpha-ketoglutrate dehydrogenase was the major fate of glutamine, flux of glutamine to lipid via reductive carboxylation of alpha-ketoglutarate was demonstrated by measuring incorporation of [5-14C]glutamine into 14C-lipid. In media containing glucose (6 mM), and glutamine (0.75 mM) 47 per cent of the lipid synthesized from substrates in the media was derived from glutamine via reductive carboxylation and 49 per cent from glucose. These findings of nearly equal fluxes suggest that lipogenesis via reductive carboxylation may be an important role of glutamine in hepatoma cells.
Mol Cell Biochem 1995 Nov 22
PMID:Glutamine metabolism in AS-30D hepatoma cells. Evidence for its conversion into lipids via reductive carboxylation. 875 Nov 55

One of the primary goals in transcription factor research is the elucidation of the genetic networks controlled by a factor or by members of a family of closely related factors. The pleiotropic effects of retinoic acid (PA) in the developing and adult animal are mediated by ligand-inducible transcription factors (RA receptors [RARs] and retinoid X receptors [RXRs]) that belong to the superfamily of nuclear receptors. Regulatory regions of PA effector genes contain RAR and RXR binding sites (RAR elements [RAREs] and RXR elements [RXREs]) that generally consist of direct or everted repeats of the core half-site motif, (A/G)G(G/T)TCA. In order to identify novel genes regulated by RA, we devised a selection strategy based on the premise that regulatory regions of a large number of housekeeping and tissue-specific genes are embodied within CpG island DNA. In this method, referred to as CpG-selected and amplified binding, fragments derived from the CpG island fraction of the murine genome are selected by a gel mobility shift assay using in vitro-transcribed and -translated RXR-RAR. Multiple rounds of selection coupled with amplification of the fragments by PCR enabled us to clone a population of CG-rich fragments of which approximately one-fifth contained consensus RAREs or RXREs. Twelve genomic fragments containing novel response elements are described, and the transcription unit associated with one of them, NN-84AG, was characterized in detail. The mouse NN-84AG transcript is upregulated by RA in F9 embryonal carcinoma cells and is homologous to an expressed sequence tag (EST41159) derived from a human infant brain cDNA library. Cloning of the murine NN8-4AG genomic sequence places the RXRE in the proximity of the transcription initiation sites of the gene. Although sequence analysis indicates that the EST41159 gene product is novel, a region of amino acid identity with sequences of a yeast polypeptide of, as yet, unknown function and the Drosophila trithorax protein suggests the presence of an evolutionarily and functionally conserved domain. Our study demonstrates that transcription factor binding sites and corresponding regulated genes can be identified by selecting fragments derived from the CpG island fraction of the genome.
Mol Cell Biol 1996 Aug
PMID:Isolation of a novel retinoic acid-responsive gene by selection of genomic fragments derived from CpG-island-enriched DNA. 875 34

Recent studies of isotope exchange across lactate dehydrogenase (LDH) and alanine aminotransferase (AAT) in hearts call into question whether both reactions are in equilibrium. To compare the oxidative and non-oxidative fates of glycolytic end products, isolated rabbit hearts were perfused with 5 mM [2-13C] glucose and 2.5 mM [3-13C] pyruvate: with (n = 6) and without (n = 7) stimulation of pyruvate oxidation using dichloroacetate (DCA), and during normal perfusion or hypoxia (n = 7/n = 6, +/- DCA). 13C NMR spectroscopy of intact hearts confirmed a steady-state enrichment level in both alanine and lactate. 1H- and 13C-NMR spectroscopy of tissue extracts identified the fractions of lactate, alanine and glutamate pools formed from each exogenous substrate. Glycolysis from glucose accounted for 22 +/- 7% of lactate formed and 10 +/- 2% of alanine formed in control hearts, and 16 +/- 2% lactate and 15 +/- 2% alanine in hypoxic hearts (mean +/- S.E.M.). In contrast, exogenous pyruvate formed 36 +/- 5% of the lactate pool, and 86 +/- 3% of the alanine pool in controls and 47 +/- 3% of lactate and of 67 +/- 3% alanine during hypoxia. [2(-13)C] glucose did not contribute to oxidative energy production via the TCA cycle as determined from low 13C enrichment of glutamate C5 from glucose (< 2%), while [3-13C] pyruvate accounted for 84 +/- 7% of labeled glutamate C4. Thus, exogenous pyruvate out-competed the metabolism of glucose, indicating low glycolytic activity. At 40 min, 96 +/- 2% of the total alanine was labeled from either glucose or pyruvate, confirming equilibrium at AAT. However, only 55 +/- 10% of total lactate was labeled, suggesting that the LDH reaction is not in rapid equilibrium within the myocardium.
J Mol Cell Cardiol 1996 May
PMID:Chemical versus isotopic equilibrium and the metabolic fate of glycolytic end products in the heart. 876 37

A single polypeptide of approx. 67 kDa mol.wt. with DNA polymerase activity has been chromatographically purified from shoot tips of 72 hr. grown germinated seedlings of rice (Oryza sativa.L.cv IR-8). An approx. 4800 fold enrichment of specific activity was measured by the incorporation of 3H-dTMP into trichloroacetic acid insoluble fraction, using activated calf thymus DNA as template-primer. The enzyme uses different types of DNA but not RNA as a template. The enzyme requires Mg+2, high KCl, and is highly sensitive to dideoxyribonucleoside triphosphate but is unaffected by aphidicolin, suggesting a plant counterpart of mammalian DNA polymerase beta. Replication of M13mp18 single stranded DNA by extension of 5'32P-labeled 17-mer primer(-40) showed distributive type of DNA synthesis by the rice DNA polymerase beta, which is a characteristic feature of mammalian DNA polymerase beta.
Biochem Mol Biol Int 1996 May
PMID:Isolation of mammalian pol beta type DNA polymerase in shoot tips of germinated seedlings of IR-8 rice (Oryza sativa L.). 879 34

The possible presence of a sucrose-phosphate synthase (SPS) activating/stabilizing factor (SAF) presumably lost during SPS purification was investigated. Rice leaf protein extracts were chromatographed in a DEAE-Sephacel column. SPS activity of previously purified rice enzyme was enhanced to different extent by aliquots of fractions from such column. The activating capacity could not be replaced by albumin, but was nullified by EDTA. When the fractions were boiled or treated with TCA, the activating capacity disappeared suggesting its proteinaceous nature. The presence of 10 microM okadaic acid had no effect on the stimulatory action of SAF on SPS denying the possibility to SAF to be a SPS-phosphatase. Although it overlaps somehow with sucrose synthase (SS) in DEAE-Sephacel fractions, the activating protein factor and SS eluted separately during Sephadex G-200 chromatography. The activating ability was saturable at a fixed SPS concentration and was able to enhance SPS activity from other plant sources. Simultaneous studies on the activities of SPS and sucrose-phosphate phosphatase (SPP), closely linked to SPS, allowed us to suggest that SAF could be SPP. The presence of SAF/SPP did not alter the affinity of SPS for its substrates but helped to reverse the Pi inhibition at low Fru-6-P concentrations. We conclude that SPS may possibly interact with SPP, contributing to a more effective sucrose synthesis.
Cell Mol Biol (Noisy-le-grand) 1996 Jul
PMID:Activation of sucrose-phosphate synthase by a protein factor/sucrose-phosphate phosphatase. 883 97

Metabolic labelling with [35S]-methionine demonstrated that generative cells of Lilium longiflorum possess their own set of mRNA and are capable of synthesising proteins independently from the vegetative cell. The isolated generative cells synthesised ten proteins, of which six were unique to these specialised cells. Isolation of generative cells from pollen grains after [35S]-methionine labelling resulted in an identical protein profile, therefore the synthesis of these proteins was not due to isolation shock. Addition of cycloheximide, abolished TCA-precipitable counts, whilst actinomycin D had no qualitative effect on the observed protein profile, indicating active translation of pre-existing mRNAs by the generative cells.
Plant Mol Biol 1996 Aug
PMID:Generative cells of Lilium longiflorum possess translatable mRNA and functional protein synthesis machinery. 884 51

Thermally aggregated, endogenous proteins of Escherichia coli form a distinct fraction, denoted S, which is separable by sucrose-density-gradient centrifugation. It was shown earlier that DnaK, DnaJ, IbpA and IbpB heat-shock proteins are associated with the S fraction. Comparison of the rise and decay of the S fraction in mutants defective for heat-shock proteases Lon (La), Clp, HtrA (DegP, Do) and in wild-type strains made studies of proteolysis and the function of the heat-shock response possible in vivo. Different timing and the extent of action of particular proteases was revealed by the initial size and decay kinetics of the S fraction. The proteases Lon, Clp, and HtrA all participated in removal of the aggregated proteins. Mutation in the gene encoding ClpB caused the most prominent effect (47% stabilization of the S fraction). The correlation between the disappearance of the S fraction and proteolytic activity was supported by the result of the in vitro reaction. Approximately one third of the isolated S fraction was converted to trichloroacetic acid-soluble products by the purified HtrA protease. Mg2+ ions stimulated the reaction, in contrast to the reaction of the HtrA protease with casein. The digestion of the aggregated proteins, unlike the digestion of casein, by HtrA protease in vitro was inhibited by added DnaJ, which might reflect protection of the aggregated proteins in vivo by DnaJ from excessive degradation. One might expect that such an activity of DnaJ would promote denatured protein renaturation versus proteolysis. Moreover, among the aggregated proteins that are discernible by electrophoresis, none could be identified as being more susceptible than any other to HtrA degradation. The separation pattern of these proteins before and after the in vitro digestion did not show a difference corresponding to the loss of about 30% of constituting proteins. This was interpreted as recognition by the HtrA protease of a state of protein denaturation rather than specific amino acid sequences in particular proteins. We conclude that the fraction consisting of proteins heat-aggregated in vivo (i.e. the S fraction) contains endogenous substrates for the heat-shock proteases tested. Their use for in vitro reaction reveals information that is in some respects different from that obtained with exogenous substrates such as casein.
Mol Microbiol 1996 Nov
PMID:Degradation by proteases Lon, Clp and HtrA, of Escherichia coli proteins aggregated in vivo by heat shock; HtrA protease action in vivo and in vitro. 893 38

Metabolic fates of pyruvate (CO2, lactate, citrate) in normal and neoplastic cells have been assessed. Pyruvate consumption by tumour cells falls (by 72-85%) and mean percentage oxidation rises from 75% to 91% with hydroxycitrate. Ratios of rates of oxidation of (3-(14)C-pyruvate) : (1-(14)C-pyruvate), indicating CO2 produced from TCA cycle activity : that from PDH activity, are higher for tumorigenic (0.17-0.24) than for non-tumorigenic (0.005-0.04) cells and increase (0.27-0.65 and 0.13-0.29, respectively) with hydroxycitrate. Although maximal ATP-citrate lyase activities do not correlate with malignancy, citrate may be a major fate of glutaminolytic pyruvate in tumour cells. Citrate accounts for 14-37% of consumed glutamine compared with 11-13% being recovered as CO2. By contrast, approximately 100% of glycolytic pyruvate is converted to lactate.
Biochem Mol Biol Int 1996 Nov
PMID:Hydroxycitrate causes altered pyruvate metabolism by tumorigenic cells. 895 95

The authors sought to determine whether developmental differences in the magnitude of embryonic mortality caused by heat stress in vivo are caused by changes in resistance of embryos to elevated temperature. In this regard, responses of oocytes, two-cell embryos, four-to eight-cell embryos, and compacted morulae to heat shock were compared. An additional goal was to define further the role of cumulus cells and glutathione in thermoprotection of oocytes. In experiment 1, heat shock (41 degrees C for 12 hr) decreased the number of embryos developing to the blastocyst stage for two-cell (26% vs. 0%) and four- to eight-cell (25% vs. 10%) embryos but did not affect morulae (37% vs. 42%). In experiment 2, exposure of two-cell embryos to 41 degrees C for 12 hr reduced the number of four- to eight-cell embryos present 24 hr after the end of heat shock (88% vs. 62%). In experiment 3, heat shock reduced the number of two-cell embryos developing to blastocyst (49% vs. 8%) but did not affect subsequent development of oocytes when heat shock occurred during the first 12 hr of maturation (46% vs. 41% development to blastocyst); membrane integrity was not altered. In experiment 4, oocytes were cultured with an inhibitor of glutathione synthesis, DL-buthionine-[S,R]-sulfoximine (BSO), for 24 hr and exposed to 41 degrees C for the first 12 hr of maturation. Percentages of blastocysts were 35% (39 degrees C), 18% (41 degrees C), 17% (39 degrees C + BSO), and 11% (41 degrees C + BSO). For experiment 5, oocytes were either denuded or left with cumulus intact and were then radiolabeled with [35S]methionine and [35S]cysteine at 39 degrees C or 41 degrees C for 12 hr. Exposure of oocytes to 41 degrees C for 12 hr reduced overall synthesis of 35S-labeled TCA-precipitable intracellular proteins (18,160 vs. 14,594 dpm/oocyte), whereas presence of cumulus increased synthesis (9,509 vs. 23,246). Analysis by two-dimensional SDS PAGE and fluorography revealed that heat shock protein 68 (HSP68) and two other putative heat shock proteins, P71 and P70, were synthesized by all oocytes regardless of treatment. Heat shock did not alter the synthesis of HSP68 or P71 but decreased amounts of newly synthesized P70. Cumulus cells increased synthesis of P71 and P70. Results indicate there is a biphasic change in resistance to elevations in temperature as oocytes mature, become fertilized, and develop. Resistance declines from the oocyte to the two-cell stage and then increases. Evidence suggests a role for cumulus cells in increasing HSP70 molecules and protein synthesis. Data also indicate a role for glutathione in oocyte function.
Mol Reprod Dev 1997 Feb
PMID:Differential responses of bovine oocytes and preimplantation embryos to heat shock. 902 45

The effect of proline on the prevention of trichloroacetic acid (TCA)-induced protein precipitation is studied. It is found that proline at high concentrations (> 4.0 M) completely prevents TCA-induced precipitation of hen egg white lysozyme. Other osmolytes such as ethylene glycol, glycerol and sucrose fail to prevent the TCA-induced precipitation of lysozyme. Viscosity and 1-anilino-8-naphthalene sulphonic acid binding experiments suggest that proline at high concentration forms an ordered supramolecular assembly. Proline is shown to increase the solubility of protein due to formation of such higher order assemblies. A model of the supra-molecular assembly of proline is proposed and a possible in vivo role of the increased levels of proline under water stress is discussed.
Biochem Mol Biol Int 1997 Feb
PMID:Proline is a protein solubilizing solute. 906 63


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