Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.4.1.1 (pyruvate carboxylase)
 1,516 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neocortical astrocytes were incubated with 13C-labeled substrates to determine metabolic pathways. 13C NMR spectroscopy was used to analyze 13C incorporation into glutamine and citrate from the different precursors--[1-13C]glucose or [2-13C]acetate. When glucose was the labeling substrate, incorporation due to pyruvate carboxylation should be observed in the C-2 position in glutamine and the C-4 position in citrate. A large incorporation due to pyruvate carboxylation was observed in glutamine in the C-2 and C-3 positions, but not in citrate. When acetate was the precursor, the labeling ratios in the C-2/C-4 positions in glutamine and in the equivalent positions in citrate were 0.27 and 0.11, respectively. Moreover, acetate labeled lactate in the C-2 position much less than did glucose. Altogether, these observations led to the conclusion that glutamine precursors and citrate are either produced in different types of astrocytes or in different tricarboxylic acid cycles, situated in functionally different mitochondria in the same cell, and that in all likelihood pyruvate carboxylase is expressed differently in these mitochondria.
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PMID:NMR spectroscopic studies of 13C acetate and 13C glucose metabolism in neocortical astrocytes: evidence for mitochondrial heterogeneity. 780 89

13C nuclear magnetic resonance spectroscopy was used to study the metabolism of [2-13C]pyruvate in intact cells of Halobacterium salinarium. The spectra of these cells show that pyruvate is reduced to lactic acid and transaminated to alanine. The intensity of C-2 lactate is higher under anaerobic conditions than under aerobic conditions. When cells are grown in the absence of glucose, the level of C-2 lactate intensity is lower. In extracts of these cells, the level of NADH-dependent lactate dehydrogenase activity is lower than that of cells grown in the presence of glucose. A C-5 glutamate resonance suggests the entry of pyruvate into the tricarboxylic acid cycle through acetyl-coenzyme A. In addition, the label is also observed at C-3 and C-4 of glutamate, signifying a pyruvate carboxylase-type reaction and scrambling of label at the fumarate-succinate stage plus malic enzyme operation, respectively. Citrate synthase and malic enzyme activity appear to be controlled by the growth conditions of H. salinarium.
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PMID:Pyruvate metabolism in Halobacterium salinarium studied by intracellular 13C nuclear magnetic resonance spectroscopy. 815 86

Nuclear magnetic resonance (NMR) was used to study the metabolic pathways involved in the conversion of glucose to glutamate, gamma-aminobutyrate (GABA), glutamine, and aspartate. D-[1-13C]Glucose was administered to rats intraperitoneally, and 6, 15, 30, or 45 min later the rats were killed and extracts from the forebrain were prepared for 13C-NMR analysis and amino acid analysis. The absolute amount of 13C present within each carbonatom pool was determined for C-2, C-3, and C-4 of glutamate, glutamine, and GABA, for C-2 and C-3 of aspartate, and for C-3 of lactate. The natural abundance 13C present in extracts from control rats was also determined for each of these compounds and for N-acetylaspartate and taurine. The pattern of labeling within glutamate and GABA indicates that these amino acids were synthesized primarily within compartments in which glucose was metabolized to pyruvate, followed by decarboxylation to acetyl-CoA for entry into the tricarboxylic acid cycle. In contrast, the labeling pattern for glutamine and aspartate indicates that appreciable amounts of these amino acids were synthesized within a compartment in which glucose was metabolized to pyruvate, followed by carboxylation to oxaloacetate. These results are consistent with the concept that pyruvate carboxylase and glutamine synthetase are glia-specific enzymes, and that this partially accounts for the unusual metabolic compartmentation in CNS tissues. The results of our study also support the concept that there are several pools of glutamate, with different metabolic turnover rates.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cerebral metabolic compartmentation as revealed by nuclear magnetic resonance analysis of D-[1-13C]glucose metabolism. 851 79

Two-dimensional 1H detected 13C NMR spectroscopy has been used to study the intracellular metabolism of [3-(13)C]pyruvate in Halobacterium salinarium. The method, resulting in considerable improvement in spectral resolution and signal-to-noise ratio, is well suited for studying transient metabolic intermediates. Pyruvate utilization by the bacterium is a double exponential function with rate constants of 49.13 and 4.67x10(-3) per min. The relative 13C enrichment is the fastest for C-3 glutamate. Glutamate C-4 labeling decreases initially and increases later on during incubation, while glutamine C-3 is high to begin with and exhibits a declining trend. The glutamate labeling indicates a high initial flux through pyruvate carboxylase and extensive randomizing of the label in the tricarboxylic acid cycle.
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PMID:A two-dimensional 1H detected 13C NMR investigation of pyruvate metabolism in Halobacterium salinarium. 950 17

Kreb's tricarboxylic (TCA) cycle was studied in Halobacterium salinarum cells grown in the presence of glucose or alanine. The cells were incubated with 13C-labeled substrate and the labeling pattern of various carbon positions in glutamate was monitored by 13C-NMR spectroscopy. [2-13C]pyruvate, when used as a substrate, led mainly to signals for C-1 and C-5 glutamate, with some C-3 glutamate. [3-13C]pyruvate as a substrate produced signals, mainly C-2, C-3, and C-4 glutamate, with some C-1 and C-5 glutamate. The multiplicity of the signals and observation of a C-1 signal in this case indicates extensive cycling of the label in the TCA cycle. Isotopomer analysis of glutamate labeling suggested that of the total pyruvate entering the TCA cycle, the flux through pyruvate:ferredoxin oxidoreductase was 90% while that through pyruvate carboxylase was 10%. Only 53% of the total acetyl-CoA was produced from the added labeled pyruvate, the rest being generated endogenously. In the presence of nitrogen, mainly transamination reaction products were formed in the case of both these substrates.
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PMID:Kreb's TCA cycle in Halobacterium salinarum investigated by 13C nuclear magnetic resonance spectroscopy. 982 32