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:2.7.11.2 (PDK1)
2,238 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism by which fatty acid addition leads to the inactivation of pyruvate dehydrogenase in intact rat liver mitochondria was investigated. In all cases the fatty acid octanoate was added to mitochondria oxidizing succinate. Addition of fatty acid caused an inactivation of pyruvate dehydrogenase in mitochondria incubated under State 3 conditions (glucose plus hexokinase), in uncoupled, oligomycin-treated mitochondria, and in rotenone-menadione-treated mitochondria, but not in uncoupled mitochondria or in mitochondria incubated under State 4 conditions. A number of metabolic conditions were found in which pyruvate dehydrogenase was inactivated concomitant with an elevation in the ATP/ADP ratio. This is consistent with the inverse relationship between the ATP/ADP ratio and the pyruvate dehydrogenase activity proposed by various laboratories. However, in several other metabolic conditions pyruvate dehydrogenase was inactivated while the ATP/ADP ratio either was unchanged or even decreased. This observation implies that there are likely other regulatory factors involved in the fatty acid-mediated inactivation of pyruvate dehydrogenase. Incubation conditions in State 3 were found in which the ATP/ADP and the acetyl-CoA/CoASH ratios remained constant and the pyruvate dehydrogenase activity was correlated inversely with the NADH/NAD+ ratio. Other State 3 conditions were found in which the ATP/ADP and the NADH/NAD+ ratios remained constant while the pyruvate dehydrogenase activity was correlated inversely with the acetyl-CoA/CoASH ratio. Further evidence supporting these experiments with intact mitochondria was the observation that the pyruvate dehydrogenase kinase activity of a mitochondrial extract was stimulated strongly by acetyl-CoA and was inhibited by NAD+ and CoASH. In contrast to acetyl-CoA, octanoyl-CoA inhibited the kinase activity. These results indicate that the inactivation of pyruvate dehydrogenase by fatty acid in isolated rat liver mitochondria may be mediated through effects of the NADH/NAD+ ratio and the acetyl-CoA/CoASH ratio on the interconversion of the active and inactive forms of the enzyme complex catalyzed by pyruvate dehydrogenase kinase and pyruvate dehydrogenase phosphatase.
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PMID:Regulation of pyruvate dehydrogenase by fatty acid in isolated rat liver mitochondria. 17 49

The proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart was decreased by alloxan-diabetes or by perfusion with media containing acetate, n-octanoate or palmitate. The total activity of the dehydrogenase was unchanged. 2. Pyruvate (5 or 25mM) or dichloroacetate (1mM) increased the proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart, presumably by inhibiting the pyruvate dehydrogenase kinase reaction. Alloxan-diabetes markedly decreased the proportion of active dehydrogenase in hearts perfused with pyruvate or dichloroacetate. 3. The total activity of pyruvate dehydrogenase in mitochondria prepared from rat heart was unchanged by diabetes. Incubation of mitochondria with 2-oxo-glutarate plus malate increased ATP and NADH concentrations and decreased the proportion of active pyruvate dehydrogenase. The decrease in active dehydrogenase was somewhat greater in mitochondria prepared from hearts of diabetic rats than in those from hearts of non-diabetic rats. Pyruvate (0.1-10 mM) or dichloroacetate (4-50 muM) increased the proportion of active dehydrogenase in isolated mitochondria presumably by inhibition of the pyruvate dehydrogenase kinase reaction. They were much less effective in mitochondria from the hearts of diabetic rats than in those of non-diabetic rats. 4. The matrix water space was increased in preparations of mitochondria from hearts of diabetic rats. Dichloroacetate was concentrated in the matrix water of mitochondria of non-diabetic rats (approx. 16-fold at 10 muM); mitochondria from hearts of diabetic rats concentrated dichloroacetate less effectively. 5. The pyruvate dehydrogenase phosphate phosphatase activity of rat hearts and of rat heart mitochondria (approx. 1-2 munit/unit of pyruvate dehydrogenase) was not affected by diabetes. 6. The rate of oxidation of [1-14C]pyruvate by rat heart mitochondria (6.85 nmol/min per mg of protein with 50 muM-pyruvate) was approx. 46% of the Vmax. value of extracted pyruvate dehydrogenase (active form). Palmitoyl-L-carnitine, which increased the ratio of [acetyl-CoA]/[CoA] 16-fold, inhibited oxidation of pyruvate by about 90% without changing the proportion of active pyruvate dehydrogenase.
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PMID:Regulation of pyruvate dehydrogenase in rat heart. Mechanism of regulation of proportions of dephosphorylated and phosphorylated enzyme by oxidation of fatty acids and ketone bodies and of effects of diabetes: role of coenzyme A, acetyl-coenzyme A and reduced and oxidized nicotinamide-adenine dinucleotide. 18 Sep 74

1. The proportion of active (dephosphorylated) pyruvate dehydrogenase in rat heart mitochondria was correlated with total concentration ratios of ATP/ADP, NADH/NAD+ and acetyl-CoA/CoA. These metabolites were measured with ATP-dependent and NADH-dependent luciferases. 2. Increase in the concentration ratio of NADH/NAD+ at constant [ATP]/[ADP] and [acetyl-CoA]/[CoA] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between mitochondria incubated with 0.4mM- or 1mM-succinate and mitochondria incubated with 0.4mM-succinate+/-rotenone. 3. Increase in the concentration ratio acetyl-CoA/CoA at constant [ATP]/[ADP] and [NADH][NAD+] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between incubations in 50 micrometer-palmitotoyl-L-carnitine and in 250 micrometer-2-oxoglutarate +50 micrometer-L-malate. 4. These findings are consistent with activation of the pyruvate dehydrogenase kinase reaction by high ratios of [NADH]/[NAD+] and of [acetyl-CoA]/[CoA]. 5. Comparison between mitochondria from hearts of diabetic and non-diabetic rats shows that phosphorylation and inactivation of pyruvate dehydrogenase is enhanced in alloxan-diabetes by some factor other than concentration ratios of ATP/ADP, NADH/NAD+ or acetyl-CoA/CoA.
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PMID:Diabetes and the control of pyruvate dehydrogenase in rat heart mitochondria by concentration ratios of adenosine triphosphate/adenosine diphosphate, of reduced/oxidized nicotinamide-adenine dinucleotide and of acetyl-coenzyme A/coenzyme A. 19 89

A physiologically and biochemically realistic model of the regulation of pyruvate dehydrogenase complex (PDH) was constructed for the perfused rat heart. It includes conversion between inactive (phospho) and active (dephospho) forms by a specific protein kinase (PDHK) and phosphoprotein phosphatase (PDHP). The activity of the tightly bound PDHK is influenced by synergistic activation/inhibition by acetyl CoA/CoASH and NADH/NAD. PDHK in this simulation was more sensitive to the fraction of ADP that was Mg2+-chelated than to the ATP-to-ADP ratio. Ca2+ stimulates binding of Mg2+-dependent PDHP to the complex; the bound enzyme was considered to be the active species. The fraction of PDH in the active form, rather than substrate and inhibitor levels, determines PDH activity under these conditions. This fraction depends on the present value and recent history of the difference between PDHK and PDHP activities. Both of these are active continuously and continuously control PDH.
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PMID:Computer simulation of metabolism in pyruvate-perfused rat heart. III. Pyruvate dehydrogenase. 47 88

We have previously shown that normal Wistar rats fed for 3 weeks with an isocaloric sucrose-rich (63%) diet (SRD) develop high levels of plasma free fatty acids and increased triacylglycerol content in the myocardium. We are now reporting that these changes are accompanied by remarkably low levels of the active form of the pyruvate dehydrogenase complex (PDHa; mean +/- SEM, 37.2% +/- 3.7% of the total activity) when compared with levels found in hearts donated by control rats fed the standard chow diet (STD; 71.0% +/- 2.8%; P less than .01). Increased concentrations of both long-chain acyl-CoA (0.21 +/- 0.03 v 0.06 +/- 0.01 mumol.g dry weight-1 found in STD; P less than .01) and acetyl-CoA (0.17 +/- 0.05 v 0.09 +/- 0.01 found in STD; P less than .01), as well as a relative decrease in coenzyme A (CoASH) (0.21 +/- 0.02 v 0.32 +/- 0.05 from STD; P = NS), resulting in an increased acetyl-CoA/CoASH ratio (0.80 +/- 0.13 v 0.29 +/- 0.03 in STD; P less than .01) may have stimulated the PDH kinase, leading in turn to an inactivation of the PDH complex. The above enzymatic and metabolic changes in the in situ heart of SRD-fed rats were still present after perfusing them for 35 minutes with a Krebs-Henseleit buffer containing 11 mmol/L glucose as the only exogenous substrate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Biochemical abnormalities in the heart of rats fed a sucrose-rich diet: is the low activity of the pyruvate dehydrogenase complex a result of increased fatty acid oxidation? 198 63

Regulation of the pyruvate dehydrogenase (PDH) complex has been demonstrated to be a key mechanism in the control of carbohydrate oxidation and conservation of glucose carbon. The effect of sterile inflammation and chronic sepsis (small and large abscess) on the activity of the PDH complex was examined in liver and skeletal muscle. Sepsis altered the proportion of PDH in the active, dephosphorylated form. In hepatic tissue, sterile inflammation leads to a 2.5-fold increase in the proportion of active PDH complex compared to fed control. The same increase in the proportion of active PDH complex was observed in rats with a small septic abscess. However, when the severity of septic episode was increased, the proportion of active PDH complex decreased relative to sterile inflammation or small septic abscess animals. A different pattern in the response to sterile inflammation and sepsis on the proportion of active PDH complex was observed in skeletal muscle compared to liver. In contrast to liver, sterile inflammation did not alter the proportion of active PDH in skeletal muscle. In addition, sepsis (either small or large septic abscess) resulted in a 3-fold decrease in the proportion of active PDH relative to fed control or sterile inflammatory animals. The decrease in the proportion of active PDH complex in sepsis was associated with a corresponding increase in the skeletal muscle acetyl-CoA/CoA ratio. The mechanism responsible for lowered PDH complex activity may have been due to increased PDH kinase activity, secondary to increased skeletal muscle acetyl-CoA/CoA ratios.
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PMID:Regulation of glucose metabolism by altered pyruvate dehydrogenase activity. I. Potential site of insulin resistance in sepsis. 352 46

Dichloroacetate (DCA) is known to prevent the phosphorylation of the pyruvate dehydrogenase complex (PDHC) by blocking the action of PDH kinase. This action allows the active PDHC to exert its effect on the metabolism of glucose, lactate and alanine to acetyl CoA. DCA has been shown to reduce serum lactate levels in humans and animals in such conditions as diabetes, phenformin-induced hepatic failure, exercise, and endotoxin-induced shock. Lactic acidosis in the brain has often been postulated as a cause of neuronal damage following ischemia and hypoxia. Therefore, we examined the effect of intravenously administered DCA (100 mg/kg) in rats that were rendered hyperglycemic by intravenous glucose (2 g/kg), and then made to undergo 15 minutes of incomplete cerebral ischemia by bilateral carotid ligation and systemic hypotension (mean arterial pressure of 50 mm Hg). DCA significantly reduced serum lactate levels pre-ischemia, but had no effect on serum lactate levels after ischemia induction. Brain levels of lactate, ATP and PCr after 15 minutes of incomplete ischemia were unaffected by DCA. We conclude that in this in-vivo model the control of PDHC activity in the brain may be different than that in the periphery, and that DCA was not effective in reducing brain tissue lactate levels.
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PMID:The effect of dichloroacetate on brain lactate levels following incomplete ischemia in the hyperglycemic rat. 371 55

The activity of the pyruvate dehydrogenase kinase, which phosphorylates and thereby inactivates the pyruvate dehydrogenase complex, was stimulated by malonyl-CoA. Treatment with [2-14C]malonyl-CoA resulted in acylation of sites in the complex. Both acylation and activation of kinase activity increased in a time-dependent manner with a parallel increase in those activities when the malonyl-CoA:CoA ratio was varied. Protein-bound acyl groups were labilized by performic acid treatment indicating their attachment to protein at thiol residues; however, the product released was volatile, which is not characteristic of malonic acid. While malonyl-CoA was initially free of acetyl-CoA, stimulation of kinase activity and acylation of sites in the complex by malonyl-CoA were shown to be contingent upon enzyme-catalyzed decarboxylation. Decarboxylation appeared to be catalyzed by a trace contaminant present in highly purified preparations of both the pyruvate and 2-oxoglutarate dehydrogenase complexes. Under conditions in which both free CoA was removed (by conversion to succinyl-CoA) and then, after various periods, free acetyl-CoA was removed (by enzymic conversion to acetyl phosphate), both acetylation of sites in the complex and activation of kinase activity increased in a time-dependent manner. Concomitantly there was a decrease in the concentration dependence for activation of the kinase by malonyl-CoA. Our results strongly support the conclusion that activation of kinase activity is associated with acylation of sites in the complex, and that, in the case of malonyl-CoA, those processes depend on enzyme-catalyzed decarboxylation.
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PMID:Mechanism of activation of bovine kidney pyruvate dehydrogenase a kinase by malonyl-CoA and enzyme-catalyzed decarboxylation of malonyl-CoA. 401 76

Increases in the amount of the active non-phosphorylated form of pyruvate dehydrogenase in rat epididymal adipose tissue, as a result of incubation with insulin, persist not only during the preparation of mitochondria but also during subsequent incubation of coupled mitochondria in the presence of respiratory substrates. No effect on insulin was found if the hormone was added directly to mitochondria in the presence or absence of added plasma membranes. Concentrations of several possible regulators of pyruvate dehydrogenase kinase (ATP, ADP, NADH, NAD+, acetyl-CoA, CoA and potassium) were measured in rat epididymal-adipose-tissue mitochondria incubated under conditions where differences in pyruvate dehydrogenase activity persist as a result of insulin action. No alterations were found, and it is suggested that inhibition of the kinase is not the principal means by which insulin activates pyruvate dehydrogenase. The intramitochondrial concentration of magnesium was also unaffected. Differences in pyruvate dehydrogenase activity in interscapular brown adipose tissue associated with manipulation of plasma insulin concentrations of cold-adapted rats were also shown to persist during the preparation and subsequent incubation of mitochondria in the presence or absence of GDP. It is pointed out that the persistence of the effect of insulin on pyruvate dehydrogenase in incubated mitochondria will facilitate the recognition of the mechanism of this action of the hormone. Evidence that the short-term action of insulin involves an increase in pyruvate dehydrogenase phosphate phosphatase activity rather than inhibition of that of pyruvate dehydrogenase kinase is discussed.
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PMID:Persistence of the effect of insulin on pyruvate dehydrogenase activity in rat white and brown adipose tissue during the preparation and subsequent incubation of mitochondria. 632 Aug 7

The presentation and treatment of a central hypoventilation syndrome in a boy with pyruvate dehydrogenase complex (PDHC) deficiency are reported. Dephosphorylated PDHC was assayed in disrupted fibroblasts after pretreatment with dichloroacetate, a pyruvate dehydrogenase kinase inhibitor. Maximal specific activity of activated patient PDHC was 10% to 30% of control values. Patient PDHC activity was not increased by alterations in concentrations of pyruvate or cofactors (thiamine pyrophosphate [TPP], coenzyme A [CoA], oxidized form of nicotinamide adenine dinucleotide [NAD+]). Clinically, normalization of plasma lactate by a high-lipid diet did not prevent slowly progressive neurologic decline. The patient manifested intermittent ataxia, episodic profound weakness, moderate psychomotor retardation, ophthalmoplegia, and retinal pigment epithelial changes. A true central hypoventilation syndrome was documented on the basis of rigorous radiologic, electrophysiologic, and pulmonary function criteria. Theophylline, progesterone, and ritalin neither altered ventilatory response to CO2 nor permitted weaning from the ventilator. In contrast, peripheral chemoreceptor stimulants (intravenous doxapram; oral almitrine) effected an acute doubling of minute ventilation with appropriate decreases in PaCO2. However, a positive response to long-term therapy with almitrine could not be unequivocally shown. It was concluded that measurement of disrupted fibroblast PDHC following dichloroacetate activation constitutes an accurate assay for PDHC deficiency. PDHC deficiency must be considered in the differential diagnosis of the central hypoventilation syndrome; this appears to be the first report of such an association. Finally, a therapeutic trial of a peripheral chemoreceptor agonist is warranted in the management of central hypoventilation syndrome.
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PMID:Central hypoventilation syndrome in pyruvate dehydrogenase complex deficiency. 643 1


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