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 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

The fate of [3-13C]alanine administered to last instar larvae of an insect Manduca sexta was investigated in vivo by 13C-NMR spectroscopy. Following injection of the isotopically substituted substrate and conversion to [3-13C]pyruvate 13C was principally incorporated into C2, C3 and C4 of glutamate and glutamine in unparasitized ad libitum-fed larvae, insects starved 48 hr prior to injection and larvae parasitized by the insect parasite Cotesia congregata. Selective labeling at C2 and C3 of glutamate/glutamine resulted from carboxylation of [3-13C]pyruvate to [2,3-13C]oxaloacetate catalyzed by pyruvate carboxylase, randomization of the label in fumarate, and synthesis of glutamate and glutamine after condensation with acetyl CoA to [2 proR,3-13C]citrate. In contrast, enrichment at C4 of glutamate and glutamine resulted from oxidation [3-13C]pyruvate to [2-13C]acetyl CoA catalyzed by pyruvate dehydrogenase followed by condensation with oxaloacetate. The ratio of enrichment (C2 + C3): C4 provided a measure of the relative contributions of the pyruvate dehydrogenase and pyruvate carboxylase catalyzed pathways of substrate utilization by the tricarboxylic acid cycle. The mean ratio was 0.6 and 0.7 in control and parasitized larvae, respectively, and 2.4 in starved insects. The latter result demonstrated that substrate utilization by the TCA cycle was markedly altered by starvation. In addition, the rate of labeled alanine metabolism was significantly reduced by starvation. The concentrations of glutamate and glutamine in the blood (hemolymph) were similar in all three groups of insects. No evidence for gluconeogenesis was observed in any group. Starved larvae incorporated label into C6 of glucose and trehalose but no complementary enrichment at C1 was observed. This result was consistent with the activity of the non-oxidative phase of the pentose phosphate pathway during which labeled glyceraldehyde-3-phosphate arising from [3-13C]alanine reacts with sedoheptulose-7-phosphate yielding erythrose-4-phosphate and [6-13C]fructose-6-phosphate catalyzed by transaldolase. Specifically labeled fructose-6-phosphate then gives rise to glucose and trehalose labeled at C6. Preliminary analysis of the hemolymph of starved insects indicated the presence of several hexose phosphates labeled at C6. The hemolymph level of trehalose was significantly reduced in both starved and parasitized insects. Lipogenesis from [3-13C]alanine was evident in unparasitized control larvae but was absent in parasitized and starved insects. The pattern of labeling in fatty acid was consistent with de novo pathway utilizing [2-13C]acetyl CoA derived by oxidation of [3-13C]alanine.
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PMID:Metabolic fate of alanine in an insect Manduca sexta: effects of starvation and parasitism. 810 Jul 13

This review highlights the importance of performing an autopsy when faced with fetal abortion or termination of pregnancy with suspicion of an inborn error of metabolism. Radiological, macroscopic and microscopic features found at autopsy as well as placental anomalies that can suggest such a diagnosis are detailed. The following metabolic disorders encountered in fetuses are discussed: lysosomal storage diseases, peroxisomal disorders, cholesterol synthesis disorders, congenital disorders of glycosylation, glycogenosis type IV, mitochondrial respiratory chain disorders, transaldolase deficiency, generalized arterial calcification of infancy, hypophosphatasia, arylsulfatase E deficiency, inborn errors of serine metabolism, asparagine synthetase deficiency, hyperphenylalaninemia, glutaric aciduria type I, non-ketotic hyperglycinemia, pyruvate dehydrogenase deficiency, pyruvate carboxylase deficiency, glutamine synthase deficiency, sulfite oxidase and molybdenum cofactor deficiency.
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PMID:Antenatal manifestations of inborn errors of metabolism: autopsy findings suggestive of a metabolic disorder. 2710 18