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)

Biotin containing carboxylases in cultured human skin fibroblasts were radioactively labeled by addition of [8,9-3H]biotin to biotin-depleted cell cultures. Three major bands were visualized by fluorography after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the fibroblast proteins. These bands corresponded to pyruvate carboxylase (Mr = 125,000), the biotin-containing subunit of methyl crotonyl-CoA carboxylase (Mr = 75,000) and the biotin-containing subunit of propionyl-CoA carboxylase (Mr = 73,000) as judged by molecular weight markers, purified carboxylase protein standards, and interaction with monospecific antisera. Four out of 5 cell lines from patients with classical pyruvate carboxylase deficiency (less than 5% of normal activity) labeled with this technique displayed a normal band in the position of pyruvate carboxylase while one cell line showed complete absence of any labeled protein in this area. These results demonstrate heterogeneity in the etiology of pyruvate carboxylase deficiency.
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PMID:[3H]biotin-labeled proteins in cultured human skin fibroblasts from patients with pyruvate carboxylase deficiency. 640 85

The aim of this work was to establish the reasons why ketone bodies, although readily oxidized, do not sustain a physiological work output of the isolated rat heart for more than 30 to 45 min (Taegtmeyer, H., et al., Biochem. J. 186, 701-711 (1980)). First, it was found that the addition of glucose or of asparagine increased the rate of acetoacetate removal by 52 and 77% respectively, and availability of oxaloacetate was one factor limiting the oxidation of acetoacetate. Second, in freeze clamped hearts perfusion with acetoacetate alone caused an increase in the tissue content of acetyl-CoA, citrate, 2-oxoglutarate and glutamate but no change in malate and a decrease in aspartate when compared with glucose as substrate. The changes of aspartate and glutamate exceeded those of 2-oxoglutarate forty times. This means that oxaloacetate formed from aspartate must have passed through the stages of the citric acid cycle to form glutamate and that there was an inhibition of the 2-oxoglutarate dehydrogenase reaction. Third, in hearts perfused with acetoacetate and propionate the accumulation of glutamate and 2-oxoglutarate as well as the decrease in aspartate were associated with a sharp drop in CoASH from 0.258 to 0.093 mumol/g dry wt. This indicates that the accumulation of CoA thioesters left insufficient mitochondrial CoASH for the 2-oxoglutarate dehydrogenase reaction. Fourth, in contrast to acetoacetate cardiac function was unimpaired with acetate plus glucose. With these substrates citrate, 2-oxoglutarate, malate and aspartate all accumulated, either due to formation of oxaloacetate by pyruvate carboxylase or transamination of glutamate with pyruvate. It appears that the changes in cardiac performance and metabolism caused by acetoacetate can be explained by a relative inhibition of the citric acid cycle at the level of 2-oxoglutarate dehydrogenase. The hypothesis is advanced that this might be due to a shortage of intramitochondrial free [CoASH], but the exact mechanism of this inhibition awaits further elucidation.
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PMID:On the inability of ketone bodies to serve as the only energy providing substrate for rat heart at physiological work load. 662 22

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

The effect of long-chain acyl-CoA on subcellular adenine nucleotide systems was studied in the intact liver cell. Long-chain acyl-CoA content was varied by varying the nutritional state (fed and starved states) or by addition of oleate. Starvation led to an increase in the mitochondrial and a decrease in the cytosolic ATP/ADP ratio in liver both in vivo and in the isolated perfused organ as compared with the fed state. The changes were reversed on re-feeding glucose in liver in vivo or on infusion of substrates (glucose, glycerol) in the perfused liver, respectively. Similar changes in mitochondrial and cytosolic ATP/ADP ratios occurred on addition of oleate, but, importantly, not with a short-chain fatty acid such as octanoate. It is concluded that long-chain acyl-CoA exerts an inhibitory effect on mitochondrial adenine nucleotide translocation in the intact cell, as was previously postulated in the literature from data obtained with isolated mitochondria. The physiological relevance with respect to pyruvate metabolism, i.e. regulation of pyruvate carboxylase and pyruvate dehydrogenase by the mitochondrial ATP/ADP ratio, is discussed.
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PMID:Effect of long-chain fatty acyl-CoA on mitochondrial and cytosolic ATP/ADP ratios in the intact liver cell. 674 76

A child with a history of episodes of metabolic acidosis was found to excrete 3-hydroxyisovaleric acid and 3-methylcrotonylglycine. These metabolites disappeared following the administration of biotin. The specific activities of propionyl CoA carboxylase, 3-methylcrotonyl CoA carboxylase and pyruvate carboxylase were found to be low in skin fibroblasts cultured in the absence of added biotin. With the addition of biotin, the specific activity of all three carboxylases returned to normal, that of 3-methylcrotonyl CoA carboxylase ahowing the greatest sensitivity to biotin.
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PMID:A combined defect of three mitochondrial carboxylases presenting as biotin-responsive 3-methylcrotonyl glycinuria and 3-hydroxyisovaleric aciduria. 676 95

We have examined genetic complementation in pyruvate carboxylase deficiency by comparing the enzyme activity in polyethylene glycol-induced heterokaryons with that in unfused mixtures of fibroblasts from three affected children. Complementation, manifested as a three- to sevenfold increase in pyruvate carboxylase activity, was observed in fusions between a biotin-responsive multiple carboxylase (pyruvate carboxylase, propionyl CoA carboxylase, and beta-methylcrotonyl CoA carboxylase) deficient fibroblast line and two other lines deficient only in pyruvate carboxylase activity. Kinetic analysis of complementing pyruvate carboxylase deficient lines, measured by the rate of restoration of enzyme activity as a function of time, revealed that maximum restoration was achieved within 10-24 hr after fusion. This profile is similar to those oberved for fusions between the multiple carboxylase deficient line and two lines deficient in propionyl CoA carboxylase activity that are known to represent different gene mutations. Although the patients with pyruvate carboxylase deficiency had similar clinica findings, our studies indicate that pyruvate carboxylase deficiency is genetically heterogeneous, with at least two distinct, probably intergenic, complementation groups.
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PMID:Evidence for two genetic complementation groups in pyruvate carboxylase-deficient human fibroblast cell lines. 677 49

Three biotin-dependent enzymes, pyruvate carboxylase (PC), propionyl CoA carboxylase (PCC), and beta-methylcrotonyl CoA carboxylase (beta MCC), were biochemically characterized in fibroblasts from two patients with neonatal multiple carboxylase deficiency. Genetic complementation analyses indicated that both cell lines, designated lines 1 and 2, were deficient in the various carboxylase activities and belonged to the bio complementation group. The activities of the three carboxylases became normal when line 2 cells were incubated in medium supplemented with biotin (1 mg/l) for 24 hrs, whereas 4-6 days were required to achieve maximum activities of PC, PCC, and beta MCC (57%, 46%, and 29% of mean normal enzyme activity, respectively) in line 1 cells incubated in medium containing up to 10 mg/1 biotin. Furthermore, PC activity in line 2 continued to increase under apparent gluconeogenic conditions in culture, but not in line 1. Thermostability studies suggested that biotin stabilizes PC and beta MCC in both cell lines. PC in line 1 cells incubated with or without biotin was less stable than that in normal or line 2 cells, and the less than normal increase of enzyme activities in line 1, especially that of PC, may represent incomplete biotination. These results indicate that there is biochemical heterogeneity within the bio complementation group. Immunotitration with antibodies prepared against purified pig heart PCC demonstrated normal quantities of cross-reacting material in both lines and no differences in the amount of this material after incubation with supplemental biotin, despite the seven- to 20-fold increase in PCC activity. Thus, the increase in carboxylase activity in both bio lines appears to represent activation of rpe-existing apocarboxylase rather than de novo enzyme synthesis. The primary defect in this form of multiple carboxylase deficiency may be in a common holocarboxylase synthetase or in biotin transport. If the defect is in the synthetase, the differences noted between the two bio lines could be explained by a difference in the enzyme's Km for biotin.
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PMID:Biochemical characterization of biotin-responsive multiple carboxylase deficiency: heterogeneity within the bio genetic complementation group. 679 61

Biotin-responsive multiple carboxylase deficiency can be categorized by clinical criteria into a neonatal-onset disorder and distinct syndrome of infantile onset. Pedigrees in each instance are consistent with autosomal recessive inheritance. For a neonatal-onset proband, the sensitivity to relative biotin deprivation and the rapid clinical response to biotin supplementation are reflected by in vitro studies. Specific activities of biotin-dependent pyruvate carboxylase, propionyl CoA carboxylase, and 1-methylcrotonyl CoA carboxylase are 0.8 to 16% of mean control values after growth of fibroblasts in intermediate and very low biotin concentrations. Following relative biotin depletion, pyruvate carboxylase activity returns to normal after only 14 hr of growth in biotin-supplemented medium. In contrast, carboxylase activities in fibroblasts of an infantile-onset proband remain normal at very low biotin concentrations, even when avidin is added to the growth medium. The clinical heterogeneity, taken together with the distinct responses of cultured skin fibroblasts to biotin deprivation in vitro, probably reflect fundamentally different etiologies for the two categories of biotin-responsive multiple carboxylase deficiency.
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PMID:Biochemical evidence for diverse etiologies in biotin-responsive multiple carboxylase deficiency. 680 81

The mechanism of inhibition of pyruvate carboxylase, pyruvate dehydrogenase, and carbamyl phosphate synthetase induced by alpha-ketoisovalerate metabolism has been investigated in isolated rat hepatocytes incubated with lactate, pyruvate, ammonia, and ornithine as substrates. Half-maximum inhibitions of flux through each of these enzyme steps were obtained with 0.3 mM alpha-ketoisovalerate. The inhibition of pyruvate carboxylase flux by alpha-ketoisovalerate was largely reversed by oleate addition, but pyruvate dehydrogenase flux was inhibited further. Inhibition of flux through pyruvate carboxylase could be attributed mainly to the fall of its allosteric activator, acetyl-CoA, with some additional effect due to inhibition by methylmalonyl-CoA. Tissue acetyl-CoA levels decrease as a result of an inhibition of the active form of pyruvate dehydrogenase. Kinetic studies with the purified pig heart pyruvate dehydrogenase complex showed that methyl-malonyl-CoA, propionyl-CoA, and isobutyryl-CoA were inhibitory, the latter noncompetitive with CoASH with an apparent Ki of 90 microM. The observed inhibition of pyruvate dehydrogenase flux correlated with increases of the acetyl-CoA/CoASH and propionyl-CoA/CoASH ratios and isobutyryl-CoA levels, while increases of the mitochondrial NADH/NAD+ ratio explained differences between the effects of alpha-ketoisovalerate and propionate. Carbamyl phosphate synthetase I purified from rat liver was shown to be inhibited directly by methylmalonyl-CoA (apparent Ki of 5 mM). Inhibition of flux through carbamyl phosphate synthetase during alpha-ketoisovalerate metabolism could be attributed both to a direct inhibitory effect of methyl-malonyl-CoA and to a diminished activation by N-acetylglutamate. Direct effects of various acyl-CoA metabolites on these key enzymes may explain symptoms of hypoglycemia and hyperammonemia observed in patients with inherited disorders of organic acid metabolism.
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PMID:Interactions between alpha-ketoisovalerate metabolism and the pathways of gluconeogenesis and urea synthesis in isolated hepatocytes. 683 25

Free magnesium and MgATP2- are required for activation of the mitochondrial enzymes pyruvate carboxylase, propionyl CoA carboxylase and beta-methylcrotonyl CoA carboxylase. Previous studies have demonstrated that free Mg2+ interacts with either a Mg2+- binding site or one of the two MgATP2- sites that are required for the allosteric activation of pyruvate carboxylase. We have shown that similar Mg2+ and MgATP2- interactions occur to activate propionyl CoA carboxylase and beta-methylcrotonyl CoA carboxylase. Thus, Mg2+ and MgATP2- activation, because it is common to structurally similar carboxylases, may constitute a general mode of carboxylase activation.
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PMID:Magnesium and magnesium adenosine triphosphate activation of human propionyl CoA carboxylase and beta-methylcrotonyl CoA carboxylase. 698 5


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