Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

The growth and the activity of some enzymes were studied in a Candida lipolytica strain 12a which did not synthesize acids in a medium with glucose under the conditions of nitrogen deficiency. The substrate was not assimilated and cyanide-resistant respiration did not develop in the strain under the conditions of profound nitrogen deficiency. The inability of cells to assimilate glucose at the stationary phase of growth resulted, apparently, from an abrupt decrease of phosphofructokinase and pyruvate dehydrogenase activities in the cells. The activities of pyruvate carboxylase and citrate synthase fell down abruptly at the same time.
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PMID:[Comparative study of Candida lipolytica yeasts with various abilities to produce citrate]. 258 47

It has been proposed that administration of non-nitrogenous precursors to glycine is necessary to realize the full potential of benzoate metabolism as a pathway for disposal of waste nitrogen during ammonia intoxication (Coude et al., Clin Chim Acta 136: 211-217, 1984). However, when glyoxylate, a keto acid precursor to glycine, was administered with benzoate 1 hr prior to a challenge of ammonia, protection against ammonia toxicity was less successful than with benzoate alone. At the cellular and subcellular levels, glyoxylate and benzoate each inhibited the urea cycle in isolated hepatocytes and pyruvate carboxylase in isolated mitochondria. The action of each drug was associated with depletion of aspartate content in isolated hepatocytes and reduction of pyruvate-dependent incorporation of CO2 into aspartate in assays with isolated mitochondria. Depression of aspartate regeneration by inhibition of pyruvate carboxylase is a likely mechanism for impairment of urea cycle activity by both drugs. In whole animals, inhibition of pyruvate carboxylase may contribute to benzoate toxicity and the adverse influence of glyoxylate on benzoate therapy.
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PMID:Potentiation of benzoate toxicity by glyoxylate. Inhibition of pyruvate carboxylase and the urea cycle. 277 12

The submitochondrial localization of the four mitochondrial enzymes associated with urea synthesis in liver of Squalus acanthias (spiny dogfish), a representative elasmobranch, was determined. Glutamine- and acetylglutamate-dependent carbamoyl-phosphate synthetase, ornithine carbamoyltransferase, glutamine synthetase, and arginase were all localized within the matrix of liver mitochondria. The subcellular and submitochondrial localization and activities of several related enzymes involved in nitrogen metabolism and gluconeogenesis in liver and dogfish are also reported. Pyruvate carboxylase and phosphoenolpyruvate carboxykinase were localized in the mitochondrial matrix. Synthesis of citrulline by isolated mitochondria from ornithine proceeds at a near optimal rate at ornithine concentrations as low as 0.08 mM. The same stoichiometry and rates of citrulline synthesis are observed when ornithine is replaced by arginine. The mitochondrial location of arginase does not appear to reflect a mechanism for regulating ornithine availability.
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PMID:Submitochondrial localization of arginase and other enzymes associated with urea synthesis and nitrogen metabolism, in liver of Squalus acanthias. 286 47

The literature concerning the metabolism of carbon and nitrogen compounds in ectomycorrhizal associations of trees is reviewed. The absorption and translocation of mineral ions by the mycelia require an energy source and a reductant which are both supplied by respiratory catabolism of carbohydrates produced by the host plant. Photosynthates are also required to generate the carbon skeletons for amino acid and carbohydrate syntheses during the growth of the mycelia. Competition for photosynthates occurs between the fungal cells and the various vegetative sinks in the host tree. The nature of carbon compounds involved in these processes, their routes of metabolism, the mechanisms of control and the partitioning of metabolites between the various sites of utilization are only poorly understood. Both ascomycetous and basidiomycetous ectomycorrhizal fungi synthesize and some, if not all, accumulate mannitol, trehalose and triglycerides. The fungal strains employ the Embden--Meyerhof pathway of glucose catabolism and the key enzymes of the pentose phosphate pathway (6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, transaldolase and transketolase). Anaplerotic CO2 fixation, via pyruvate carboxylase and/or phosphoenolpyruvate carboxykinase, provides high pools of amino acids. This process could be important in the recapture and assimilation of respired CO2 in the rhizosphere. The ectomycorrhizas are thought to contain the Embden--Meyerhof pathway, the pentose phosphate pathway and the tricarboxylic acid cycle, which provide the carbon skeletons for the assimilation of ammonia into amino acids. The main route of assimilation of ammonia appears to be through the glutamine synthetase-glutamate synthase cycle in the ectomycorrhizas. Glutamate dehydrogenase plays a minor role in this process. Glutamate dehydrogenase and glutamine synthetase are present in free-living ectomycorrhizal fungi and they participate in the assimilation of ammonia and the synthesis of amino acids through the glutamate dehydrogenase/glutamine synthetase sequence. In both in vitro cultures of fungi and ectomycorrhizas, the assimilated nitrogen accumulates in glutamine. Glutamine, but also ammonia, are thought to be exported from the fungal tissues to the host cells. Studies on the metabolism of ectomycorrhizas and ectomycorrhizal fungi have focused on the metabolic pathways and compounds which accumulate in the symbiotic tissues. Studies on regulation of the overall process, and the control of enzyme activity in particular, are still fragmentary.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Carbon and nitrogen metabolism in ectomycorrhizal fungi and ectomycorrhizas. 312 Jul 92

When baker's yeast grown aerobically on ethanol as a carbon source was anaerobically cultured in a medium containing glucose, the activity of a cytoplasmic fumarate reductase irreversibly catalyzing the conversion of fumarate to succinate increased, reaching about 3 times the original activity after 12 h, while the activity of succinate dehydrogenase was almost lost after 10 h. These results indicate that the citrate cycle is partially modified to become a reductive pathway leading to succinate during the anaerobic cultivation. In non-proliferating cells grown anaerobically on glucose, the rates of accumulating succinate and pyruvate were decreased and increased, respectively, with increasing concentrations of L-aspartate or NH4Cl in the medium containing glucose as a substrate. These changes were accompanied with increase in the cellular content of aspartate, an inhibitor of pyruvate carboxylase that is involved in supplying the intermediates of the citrate cycle, and pyruvate, a substrate of the enzyme. The aminotransferase inhibitor, aminooxyacetate, prevented the changes in succinate accumulation and cellular aspartate following the addition of NH4Cl. The addition of L-glutamate caused a marked increase in the rate of succinate accumulation without changing the cellular content of aspartate. Neither L-glutamate nor L-aspartate had the ability to produce succinate. The rate of glucose consumption was not changed upon adding these nitrogen compounds. Similar findings were also observed in experiments using proliferating cells. This report presents evidence that in cells containing a large amount of the fumarate reductase, the production of succinate from glucose is regulated by the cellular level of aspartate through the pyruvate carboxylase reaction and that glutamate regulates the succinate production by a mechanism distinct from that involved in the regulation by L-aspartate.
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PMID:Regulation of reductive production of succinate under anaerobic conditions in baker's yeast. 332 98

The role of thyroid hormones in the metabolic adaptation to starvation was investigated in vivo. Glucose production, measured by tracer technique, was enhanced in hyperthyroid (185%) and reduced in hypothyroid (39%) 48-hour starved rats (euthyroid control = 100%). Urinary nitrogen excretion was increased in hyperthyroidism (132%) and decreased in hypothyroidism (70%). Compared with euthyroid controls (=100%) significant alterations for the following regulatory parameters of hepatic gluconeogenesis were observed: 1) tissue cAMP (124%/91%) and protein kinase activation (132%/90%), with a corresponding crossover between pyruvate and P-enolpyruvate (-/+/+/-); 2) pyruvate carboxylase (165%/60%), P-enolpyruvate carboxykinase (140%/82%) and fructose-1.6-bis-P-phosphatase activity (99%/61%), and 3) tissue content of the glucogenic amino acids: alanine (187%/66%) and glutamate (187%/88%), aspartate (179%/68%) and glutamate (137%/75%), as well as of oxaloacetate (254%/66%) and malate (164%/104%). The observed alterations in hepatic oligomycine-sensitive oxygen consumption in hyper- (161%) and hypothyroidism (51%) were related to the measured concentration of the intermediates of the citric acid cycle, the energy state and the mitochondrial redox state. In summary, the different rates of hepatic glucose production in hyper- and hypothyroid starved rats observed in vivo can be ascribed to 1) cAMP content, 2) gluconeogenic key enzyme activities, 3) glucogenic precursor supply and 4) cofactor (ATP) availability.
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PMID:Starvation-induced changes of hepatic glucose metabolism in hypo- and hyperthyroid rats in vivo. 626 36

Fatty liver and kidney syndrome (FLKS), a naturally occurring but experimentally reproducible disease in chickens, has several clinical, pathological, and biochemical features in common with Reye's syndrome. Because of this, it has been suggested that FLKS may serve as an animal model of Reye's syndrome. We have examined, therefore, various parameters characteristic of Reye's syndrome in chickens affected with FLKS to further delineate the similarities and differences between the two disorders. Plasma glucose concentrations were significantly lower in chickens affected with FLKS which may be caused by the significantly reduced activity of pyruvate carboxylase in all FLKS-affected animals. The activity of propionyl CoA carboxylase was low in only the most severely affected chickens, and beta-methylcrotonyl CoA carboxylase showed no difference when compared with controls. This may be due to variable sensitivities of the three carboxylases to marginal biotin deficiency which occurs with FLKS. Plasma ammonia concentrations and activities of glutamic oxaloacetic transaminase and glutamic pyruvic transaminase, however, were not elevated in the affected birds. Histological changes in the liver and kidney were noted in affected chickens, but these changes were not identical with those observed in Reye's syndrome. Although the mechanisms of nitrogen elimination in fowl differ from those in humans, failure to demonstrate hyperammonemia, elevated serum transaminase activities, or similar histological changes in tissues of affected birds indicates that FLKS is not an appropriate model for the study of Reye's syndrome.
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PMID:Fatty liver and kidney syndrome in chickens as an animal model for Reye's syndrome. 664 49

Twenty-four pigs were weaned at four weeks of age and fed either spray dried egg albumen (DA) or autoclaved DA (ADA) as the only protein source were used to evaluate plasma and hepatic parameters as indicators of biotin status. Pigs were fed one of four semipurified diets during the 42-day study: DA basal, DA + 1.1 g sulfamethazine/day (DA + S), ADA basal or ADA + .5 mg biotin/day (ADA + H). Autoclaving DA at 121 degrees C for 30 minutes reduced both the biotin binding properties of the avidin fraction and the trypsin inhibitor activity of DA. Pigs fed ADA and ADA + H had greater (P less than .05) liver pyruvate carboxylase (EC 6.4.1.1) activity and DNA concentrations, lower (P less than .05) plasma urea nitrogen levels and greater and more efficient (P less than .05) weight gain than either DA or DA + S fed pigs. Biotin supplementation further enhanced (P less than .05) liver DNA concentration but had no effect on the liver levels of RNA or total protein. Plasma levels of glucose and free fatty acids or blood levels of lactate and pyruvate were not influenced by the addition of biotin to the ADA basal diet.
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PMID:The biotin status of weanling pigs fed semipurified diets as evaluated by plasma and hepatic parameters. 685 58

The connection between the kinetics of citrate-isocitrate overproduction by Saccharomycopsis lipolytica in glucose media and the specific activities of the enzymes being related to overproduction has been investigated. The specific activities of citrate synthase, aconitate hydratase, NAD+-linked and NADP+-linked isocitrate dehydrogenase decline significantly after exhaustion of the nitrogen source, whereas the activity of the pyruvate carboxylase remains relatively constant and corresponds to changes of the production rate. The results are compared with those obtained by fermentations in n-alkane media and discussed in relation to mechanisms of overproduction.
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PMID:[Enzymatic study of citrate-isocitrate accumulation in yeast with glucose as the carbon source]. 686 52

Fatty acids produced a stimulation of gluconeogenesis and either inhibition or no effect on ureagenesis in livers perfused with gluconeogenic substrates and having NH4Cl plus ornithine as the nitrogen source. This finding indicates that stimulation of flux through pyruvate carboxylase is not sufficient to enhance urea production from ammonia. The metabolic action of fatty acids showed the following characteristics: (1) it was concentration-dependent, showing saturation-type kinetics similar to those described for fatty acid oxidation; (2) the stimulatory action on gluconeogenesis was constant and independent of NH4Cl concentration, whereas the inhibition of ureagenesis was variable and dependent on NH4Cl concentration and the degree of reduction of the gluconeogenic substrate; and (3) fatty acids produced apparent reciprocal changes in the state of reduction of the cytosolic and mitochondrial NAD systems. Fatty acid oxidation exerted its effect mainly, if not exclusively, by preventing the gluconeogenic substrate-induced stimulation of ureagenesis. Fatty acids also inhibited ureagenesis without stimulating gluconeogenesis (lactate < 1 mmol/L), ruling out a limiting energy availability as the cause of the inhibition. One or both of the following two mechanisms seem to account for the fatty acid-induced inhibition of ureagenesis from NH4Cl. First, a decreased uptake of ornithine, and second, decreased flux through pyruvate dehydrogenase and probably other NAD(P)-linked mitochondrial dehydrogenases. The correlation found between the ability of fatty acids to inhibit ureagenesis and the state of activation of pyruvate dehydrogenase supports the latter point.
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PMID:Reciprocal changes in gluconeogenesis and ureagenesis induced by fatty acid oxidation. 824 72


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