Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pyruvate Dehydrogenase Complex”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed1997

Brain energy metabolizing enzymes in Alzheimer's disease: alpha-ketoglutarate dehydrogenase complex and cytochrome oxidase.

PET observations of reduced cerebral glucose metabolism in AD could be explained by a defect in key energy metabolizing enzymes. In particular, levels of two enzymes, cytochrome oxidase (CO) and alpha-ketoglutarate dehydrogenase complex (alpha KGDHC) are generally assumed to be reliably reduced in postmortem brain of patients with AD. How strong is the evidence that brain CO and alpha KGDHC are reduced in AD? In our study CO activity and alpha KGDHC activity and protein subunit levels were measured in cerebral cortex of 19-29 AD patients and 29 control subjects. We found that mean CO activity in cerebral cortex was reduced by 16-26% in the AD group but with almost complete overlap between control and patient ranges. Since our publication in 1992, mean brain CO activity in AD was modestly reduced in 9 independent studies (p < 0.05 in 5). Activity of alpha KGDHC varied widely in control/AD subjects and is not useful as an enzyme marker. Cerebral cortical protein levels of E1-3 subunits, which showed much less variance, were reduced by 23-41% but with large overlap between control/patient groups. We concluded that decreased (i.e., below normal) brain CO and alpha KGDHC is a feature of some, but not all patients with AD. The possible causes and significance of the enzyme changes are discussed.

Alzheimer Disease↗
PubMed1991

Fraction of hepatic cytosolic acetyl-CoA derived from glucose in vivo: relation to PDH phosphorylation state.

We measured the contribution of glucose to hepatic cytosolic acetyl-CoA in vivo in rats and compared it with the phosphorylation state of a potentially regulatory enzyme complex [pyruvate dehydrogenase (PDH)]. Xenobiotic probes were used to sample hepatic cytosolic acetyl-CoA [acetylated sulfamethoxazole (SMX)] and UDP-glucose (glucuronidated acetaminophen) in vivo during [U-14C]glucose infusions. Percent active (dephosphorylated) form of PDH (PDHa) was determined on freeze-clamped liver. First, we confirmed using liver cell elutriation that acetylation of SMX occurs in parenchymal hepatocytes. Next, the fraction of cytosolic acetyl-CoA derived from [14C]glucose in vivo was shown to depend on dietary state. Specific activity of acetyl-CoA relative to plasma glucose or hepatic UDP-glucose was lower after 48 h fasting than after overnight fasting, and glucose refeeding (25 mg.kg-1.min-1 iv) maximally increased [14C]-glucose fractional contribution to acetyl-CoA within 2 h in the overnight-fasted but not in the prolonged fasted group. Hepatic PDHa demonstrated a similar but not identical pattern. The isotopic and enzymatic parameters showed significant correlations (r2 = 0.61 in 48-h fasted-refed group, r2 = 0.28 in overnight-fasted refed group), although [14C]glucose contribution to acetyl-CoA increased disproportionately compared with PDHa as refeeding progressed. The indirect pathway of UDP-glucose synthesis correlated inversely with the fractional contribution of glucose to acetyl-CoA. In summary, the fraction of hepatic acetyl-CoA derived from glucose in vivo is influenced by acute and chronic dietary factors and is only partially explained by PDHa. Regulation of the carbon source of hepatic acetyl-CoA in vivo and interactions suggested by these results (e.g., glucose-fatty acid cycle; branch-point regulation of glucose recycling) can be addressed in a quantitative fashion using this experimental framework.

Acetyl Coenzyme A↗
PubMed1992

The role of the matrix calcium level in the enhancement of mitochondrial pyruvate carboxylation by glucagon pretreatment.

The effect of Ca2+ on the rate of pyruvate carboxylation was studied in liver mitochondria from control and glucagon-treated rats, prepared under conditions that maintain low Ca2+ levels (1-3 nmol/mg of protein). When the matrix-free [Ca2+] was low (less than 100 nM), the rate of pyruvate carboxylation was not significantly different in mitochondria from control and glucagon-treated rats. Accumulation of 5-8 nmol of Ca2+/mg, which increased the matrix [Ca2+] to 2-5 microM in both preparations, significantly enhanced pyruvate carboxylase flux by 20-30% in the mitochondria from glucagon-treated rats, but had little effect in control preparations. Higher levels of Ca2+ (up to 75 nmol/mg) inhibited pyruvate carboxylation in both preparations, but the difference between the mitochondria from control and glucagon-treated animals was maintained. The enhancement of pyruvate dehydrogenase flux by mitochondrial Ca2+ uptake was also significantly greater in mitochondria from glucagon-treated rats. These differential effects of Ca2+ uptake on enzyme fluxes did not correlate with changes in the mitochondrial ATP/ADP ratio, the pyrophosphate level, or the matrix volume. Arsenite completely prevented 14CO2 incorporation when pyruvate was the only substrate, but caused only partial inhibition when succinate and acetyl carnitine were present as alternative sources of energy and acetyl-CoA. Under these conditions, mitochondria from glucagon-treated rats were less sensitive to arsenite than the control preparations, even at low Ca2+ levels. We conclude that the Ca(2+)-dependent enhancement of pyruvate carboxylation in mitochondria from glucagon-treated rats is a secondary consequence of pyruvate dehydrogenase activation; glucagon treatment is suggested to affect the conditions in the mitochondria that change the sensitivity of the pyruvate dehydrogenase complex to dephosphorylation by the Ca(2+)-sensitive pyruvate dehydrogenase phosphatase.

Adenosine Diphosphate↗
PubMed1985

Defective intramitochondrial NADH oxidation in skin fibroblasts from an infant with fatal neonatal lacticacidemia.

A small-for-gestational-age female infant born at term developed severe lactic acidosis and died on day 13 of life. Two previous sibs had also died of overwhelming lactic acidosis in the neonatal period. The lactate-to-pyruvate and 3-hydroxybutyrate-to-acetoacetate ratios were elevated at 136 and 42 to one, respectively. The activities of the pyruvate dehydrogenase complex and pyruvate carboxylase in cultured skin fibroblasts were normal but a defect in respiration was indicated by the low rates of conversion of 1-[14C]pyruvate, glutamate, and lactate to 14CO2 in these cells. Skin fibroblast cultures also displayed an elevated lactate-to-pyruvate ratio (72:1) when incubated with glucose as substrate compared to control cell cultures (20:1). When mitochondrial preparations of skin fibroblasts (prepared by digitonin extraction) were tested for their ability to synthesize ATP from a variety of substrates, it was found that those of the patient made adequate amounts of ATP with either succinate or ascorbate/tetramethyl-phenylenediamine as substrate but not with the NAD-linked substrates pyruvate, isocitrate, and palmitoyl carnitine. We propose that this is indicative of a defect in the respiratory chain between NADH and coenzyme Q, for the first time demonstrable in cultured skin fibroblasts.

Acidosis↗
PubMed2001

Regulation of pyruvate dehydrogenase activity through phosphorylation at multiple sites.

The enzymic activity of the mammalian pyruvate dehydrogenase complex is regulated by the phosphorylation of three serine residues (sites 1, 2 and 3) located on the E1 component of the complex. Here we report that the four isoenzymes of protein kinase responsible for the phosphorylation and inactivation of pyruvate dehydrogenase (PDK1, PDK2, PDK3 and PDK4) differ in their abilities to phosphorylate the enzyme. PDK1 can phosphorylate all three sites, whereas PDK2, PDK3 and PDK4 each phosphorylate only site 1 and site 2. Although PDK2 phosphorylates site 1 and 2, it incorporates less phosphate in site 2 than PDK3 or PDK4. As a result, the amount of phosphate incorporated by each isoenzyme decreases in the order PDK1>PDK3>or=PDK4>PDK2. Significantly, binding of the coenzyme thiamin pyrophosphate to pyruvate dehydrogenase alters the rates and stoichiometries of phosphorylation of the individual sites. First, the rate of phosphorylation of site 1 by all isoenzymes of kinase is decreased. Secondly, thiamin pyrophosphate markedly decreases the amount of phosphate that PDK1 incorporates in sites 2 and 3 and that PDK2 incorporates in site 2. In contrast, the coenzyme does not significantly affect the total amount of phosphate incorporated in site 2 by PDK3 and PDK4, but instead decreases the rate of phosphorylation of this site. Furthermore, pyruvate dehydrogenase complex phosphorylated by the individual isoenzymes of kinase is reactivated at different rates by pyruvate dehydrogenase phosphatase. Both isoenzymes of phosphatase (PDP1 and PDP2) readily reactivate the complex phosphorylated by PDK2. When pyruvate dehydrogenase is phosphorylated by other isoenzymes, the rates of reactivation decrease in the order PDK4>or=PDK3>PDK1. Taken together, results reported here strongly suggest that the major determinants of the activity state of pyruvate dehydrogenase in mammalian tissues include the phosphorylation site specificity of isoenzymes of kinase in addition to the absolute amounts of kinase and phosphatase protein expressed in mitochondria.

Adenosine Triphosphate↗
PubMed1988

Is the nephrotoxicity of (R)-3-chlorolactate in the rat caused by 3-chloropyruvate?

1. When (R, S)-[3-36 Cl]chlorolactate was administered to male rats, two radioactive constituents were excreted in the urine. These were identified as 36Cl- and [3-36 Cl]chlorolactate which was subsequently shown to be essentially the (S)-isomer. 2. Analysis of the urinary oxalate content from rats receiving either (R)- or (S)-3-chlorolactate revealed that elevated levels were produced by the (R)-isomer whereas normal levels followed the administration of the (S)-isomer. 3. Treatment of (R,S)-3-chlorolactate with a modified Fenton's oxidizing system produced oxalate and an intermediate which was identified as 3-chloropyruvate. 4. 3-Chloropyruvate is a potent nephrotoxin in the rat producing a brief phase of diuresis when administered, increasing the urinary excretion of oxalate and inhibiting the oxidative metabolic capability of rat kidney tubules and rat kidney mitochondria in vitro. 5. Both (R)-3-chlorolactate and 3-chloropyruvate were shown to be inhibitors of the commercially-available pyruvate dehydrogenase complex. 6. 3-Chloropyruvate inhibits kidney mitochondrial metabolism possibly at the pyruvate dehydrogenase complex level and appears to be a metabolite of (R)- but not (S)-3-chlorolactate.

Animals↗
PubMed1985

alpha-Ketoacid dehydrogenase complexes and respiratory fuel utilisation in diabetes.

Activity of the pyruvate dehydrogenase complex determines the rate of glucose oxidation in animals including man. The complex is regulated by reversible phosphorylation, phosphorylation resulting in inactivation. Activity is therefore dependent upon the activities of pyruvate dehydrogenase kinase and phosphatase. Activity of the complex is reduced in diabetes and starvation as a result of insulin deficiency. The mechanism involves activation of pyruvate dehydrogenase kinase by short-term effects of products of fatty acid oxidation and by longer term effects involving specific protein synthesis; in hepatocytes the signals may include lipid fuels and glucagon. Activity of the branched chain ketoacid dehydrogenase complex determines the rate of degradation of branched chain aminoacids which is adjusted according to dietary supply. The complex is regulated by reversible phosphorylation, phosphorylation being inactivating. In liver and kidney, but not in muscles a protein activator (free E1 component) may reactivate phosphorylated complex without dephosphorylation and facilitate hepatic oxidation of branched chain ketoacids. Metabolic adjustments induced by diet and diabetes include loss of activator protein, loss of total complex activity in liver but not muscles, and enhanced inactivation by phosphorylation in liver.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1999

Lipoamide dehydrogenase deficiency due to a novel mutation in the interface domain.

An infant with a neurodegenerative disorder accompanied by lactic acidemia is described. In muscle homogenate, the activity of lipoamide dehydrogenase (LAD), the third catalytic subunit of pyruvate dehydrogenase complex (PDHc), alpha-ketoglutarate dehydrogenase complex (KGDHc), and branched-chain keto acid dehydrogenase complex was reduced to 15% of the control. The activity of PDHc was undetectable and the activity of KGDHc was 2% of the control mean. The immunoreactive LAD protein was reduced to about 10% of the control. Direct sequencing of LAD cDNA revealed only one mutation, substituting Asp for Val at position 479 of the precursor form. The mutation resides within the interface domain and likely perturbs stable dimerization. The phenotypic heterogeneity in LAD deficiency is not directly correlated with the residual LAD activity but rather with its impact on the multienzymatic complex activity.

Amino Acid Sequence↗
PubMed1993

X chromosome inactivation and the diagnosis of X linked disease in females.

In studies of female patients with suspected deficiency of the E1 alpha subunit of the pyruvate dehydrogenase complex, we have found that X inactivation ratios of 80:20 or greater occur at sufficient frequency in cultured fibroblasts to make exclusion of the diagnosis impossible in about 25% of cases. Pyruvate dehydrogenase E1 alpha subunit deficiency is an X linked inborn error of metabolism which is well defined biochemically and is unusual in that most heterozygous females manifest the condition. The diagnosis is usually established by measurement of enzyme activity and the level of immunoreactive protein and these analyses are most commonly performed on cultured fibroblasts from the patients. Skewed patterns of X chromosome inactivation make it impossible to exclude the diagnosis if the normal X chromosome is expressed in the majority of cells. While most of the observed variation appears to be the expected consequence of random X inactivation, it may be further exaggerated by sampling and subsequent expansion of the cells for analysis.

Cells, Cultured↗
PubMed1992

Conformational studies of the interdomain linker peptides in the dihydrolipoyl acetyltransferase component of the pyruvate dehydrogenase multienzyme complex of Escherichia coli.

Two peptides (PEP1, 26 residues, and PEP2, 22 residues) were synthesized with amino acid sequences identical to two of the long segments of polypeptide chain rich in alanine, proline, and charged amino acids that link the lipoyl domains together in the dihydrolipoyl acetyltransferase component of the pyruvate dehydrogenase multienzyme complex of Escherichia coli. The circular dichroism and 400-MHz 1H NMR spectra of the peptides indicated that they lacked regular secondary structure. Even in the presence of 45% (v/v) hexafluoroisopropanol, they appeared to acquire a helical content of only 23-25%. However, 13C NMR spectroscopy revealed that the Ala-Pro peptide bonds were all (> 95%) in the trans configuration, compared with a value of 87% for the Ala-Pro bond in the model peptide AAPA, which is a recurrent sequence motif in PEP1 and PEP2. Likewise in peptides representing the N- and C-terminal halves of peptide PEP2, the Ala-Pro bonds were again all (> 95%)-trans, suggesting that peptide length is the essential determinant of the cis:trans ratio. Antisera were raised against peptides PEP2 and PEP3, the latter representing a third interdomain segment of polypeptide chain (Radford, S. E., Laue, E. D., Perham, R. N., Martin, S. R., and Appella, E. (1989a) J. Biol. Chem. 264, 767-775). Despite extensive sequence similarity among peptides PEP1, PEP2, and PEP3, only limited immunological cross-reactivity was observed, which suggests that the antigenic epitope(s) in the peptides are different and distinct. It is likely that these peptides are representative of a class of inter-domain linkers or spacers found in a wide variety of proteins and endowed with varying degrees of flexibility and stiffness to match their particular biological purpose.

Acetyltransferases↗
PubMed1998

Kinetics and specificity of reductive acylation of wild-type and mutated lipoyl domains of 2-oxo-acid dehydrogenase complexes from Azotobacter vinelandii.

The kinetics and specificity of reductive acylation of lipoyl domains derived from Azotobacter vinelandii 2-oxo-acid dehydrogenase complexes, catalysed by A. vinelandii and Escherichia coli complexes, have been investigated. With the wild-type pyruvate dehydrogenase complex from A. vinelandii the rate of reductive acetylation and deacetylation was studied by rapid mixing methods. The rate of reductive acetylation, 126 s(-1), corresponds well with the turnover rate derived from steady-state measurements. Deacetylation was rapid and specific for coenzyme A. No deacetylation was observed with reduced or oxidised lipoamide or with dithiothreitol. The rate of reductive acetylation of complex-bound lipoyl domains by pyruvate dehydrogenase (E1p) is at least 60 times higher than of free lipoyl domains under comparable conditions. This gain in catalytic rate indicates a large diffusion limitation of lipoyl domains when attached via the flexible linker segments to the complex, and illustrates the efficiency of substrate channeling in the multienzyme complex. The 2-oxo-acid dehydrogenases exhibit specificity for lipoyl domains in the reductive acylation reaction. The A. vinelandii lipoyl domain derived from the pyruvate dehydrogenase complex is a good substrate for A. vinelandii E1p, but not for A. vinelandii 2-oxoglutarate dehydrogenase (E1o), and vice versa. The A. vinelandii lipoyl domain of the pyruvate dehydrogenase complex is also, although at a lower rate, reductively acetylated by E. coli E1p and reductively succinylated by E. coli E1o. Likewise, the A. vinelandii lipoyl domain derived from the 2-oxoglutarate dehydrogenase complex is recognised by E. coli E1o, but not by E. coli E1p. This suggests that common determinants of the lipoyl domains exist that are responsible for recognition by the E1 components. On the basis of the observed specificity and lipoyl domain sequences and structures, an exposed loop of the A. vinelandii 2-oxoglutarate dehydrogenase complex lipoyl domain was subjected to mutagenesis. Although the reductive acylation experiments of mutants of the lipoyl domain indicate the importance of this loop for recognition, it is probably not the single determinant for specificity.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1980

Acetyl-CoA synthesizing enzymes in cholinergic nerve terminals.

The activities of five enzymes involved in acetyl-CoA synthesis, pyruvate dehydrogenase complex, ATP citrate lyase, carnitine acetyltransferase, acetyl-CoA synthetase, and citrate synthase, were determined in normal nucleus interpeduncularis and nucleus interpeduncularis in which cholinergic terminals were removed following lesion of the habenulointerpeduncular tract. The activities of aspartate transaminase, fumarase, and GABA transaminase also were determined to compare the effect of lesion on other mitochondrial enzymes which are not linked to the biosynthesis of ACh. In normal nucleus interpeduncularis the activities of carnitine acetyltransferase and pyruvate dehydrogenase complex were higher than the activity of ChAT (choline acetyltransferase), whereas the activities of acetyl-CoA synthetase and citrate synthase were considerably lower than that of ChAT. The effect of the lesion separated the enzymes into two groups: the activities of pyruvate dehydrogenase complex, carnitine acetyltransferase, fumarase and aspartate transaminase decreased by 30--40%, whereas the activities of the other enzymes descreased 5--15%. ChAT activity was in all cases less than 15% of normal. It could be concluded that none of the acetyl-CoA synthesizing enzymes decreased to the degree that ChAT did. Only pyruvate dehydrogenase complex and carnitine acetyltransferase seem to be localized in cholinergic terminals to a significant degree. ATP citrate lyase as well as acetyl-CoA synthetase seem to have less significance in supporting acetyl-CoA formation in cholinergic nerve terminals.

4-Aminobutyrate Transaminase↗
PubMed2005

Cloning of the rat pyruvate dehydrogenase kinase 4 gene promoter: activation of pyruvate dehydrogenase kinase 4 by the peroxisome proliferator-activated receptor gamma coactivator.

The pyruvate dehydrogenase complex catalyzes the conversion of pyruvate to acetyl-CoA in mitochondria and is a key regulatory enzyme in the metabolism of glucose to acetyl-CoA. Phosphorylation of pyruvate dehydrogenase by the pyruvate dehydrogenase kinases (PDK) inhibits pyruvate dehydrogenase complex activity. There are four PDK isoforms, and expression of PDK4 and PDK2 genes is elevated in starvation and diabetes, allowing glucose to be conserved while fatty acid oxidation is increased. In these studies we have investigated the transcriptional mechanisms by which the expression of the PDK4 gene is increased. The peroxisome proliferator-activated receptor gamma coactivator (PGC-1alpha) stimulates the expression of genes involved in hepatic gluconeogenesis and mitochondrial fatty acid oxidation. We have found that PGC-1alpha will induce the expression of both the PDK2 and PDK4 genes in primary rat hepatocytes and ventricular myocytes. We cloned the promoter for the rat PDK4 gene. Hepatic nuclear factor 4 (HNF4), which activates many genes in the liver, will induce PDK4 expression. Although HNF4 and PGC-1alpha interact to stimulate several genes encoding gluconeogenic enzymes, the induction of PDK4 does not involve interactions of PGC-1alpha with HNF4. Using the chromatin immunoprecipitation assay, we have demonstrated that HNF4 and PGC-1alpha are associated with the PDK4 gene in vivo. Our data suggest that by inducing PDK genes PGC-1alpha will direct pyruvate away from metabolism into acetyl-CoA and toward the formation of oxaloacetate and into the gluconeogenic pathway.

Animals↗
PubMed1978

Regulation of pig heart pyruvate dehydrogenase by phosphorylation. Studies on the subunit and phosphorylation stoicheiometries.

1. The molecular weights of the subunits of purified pig heart pyruvate dehydrogenase complex were determined by sodium dodecyl sulphate/polyacrylamide-disc-gel electrophoresis and were: pyruvate decarboxylase, alpha-subunit 40600, beta-subunit 35100; dihydrolipoyl acetyltransferase 76100; dihydrolipoyl dehydrogenase 58200. 2. Inactivation of the pyruvate dehydrogenase complex by its integral kinase corresponded to the incorporation of 0.46nmol of P/unit of complex activity inactivated. 3. Further incorporation of phosphate into the complex occurred to a limit of 1.27nmol of P/unit of complex inactivated (approx. 3 times that required for inactivation). 4. Phosphate was incorporated only into the alpha-subunit of the decarboxylase. 5. The molar ratio of phosphate to alpha-subunits of the decarboxylase was estimated by radioamidination of amino groups of pyruvate dehydrogenase [(32)P]phosphate complex by using methyl [1-(14)C]acetimidate, followed by separation of alpha-subunits by sodium dodecyl sulphate/polyacrylamide-disc-gel electrophoresis. Inactivation of the complex (0.46nmol of P/unit of complex inactivated) corresponded to a molar ratio of one phosphate group per two alpha-chains (i.e. one phosphate group/alpha(2)beta(2) tetramer). Complete phosphorylation corresponded to three phosphate groups per alpha(2)beta(2) tetramer. 6. Subunit molar ratios in the complex were also estimated by the radioamidination technique. Results corresponded most closely to molar ratios of 4 alpha-subunits:4 beta-subunits:2 dihydrolipoyl acetyltransferase subunits:1 dihydrolipoyl dehydrogenase subunit.

Chemical Phenomena↗
PubMed2005

Thiamine-responsive congenital lactic acidosis: clinical and biochemical studies.

We studied six infants with thiamine-responsive congenital lactic acidosis and normal pyruvate dehydrogenase complex activity in vitro, through clinical and biochemical analysis. In addition to elevated lactate and pyruvate levels, the data revealed increased urinary excretion of alpha-ketoglutarate, alpha-ketoadipate, and branched chain ketoacids, indicating functional impairment of thiamine-requiring enzymes, such as pyruvate dehydrogenase complex, alpha-ketoglutarate dehydrogenase complex, alpha-ketoadipate dehydrogenase, and branched chain amino acid dehydrogenase. The metabolism of thiamine has not been investigated in patients with thiamine-responsive congenital lactic acidosis. We evaluated two specific transport systems, THTR-1 (SLC19A2) and THTR-2 (SLC19A3), and a pyrophosphorylating enzyme of thiamine, thiamine pyrophosphokinase (hTPK 1), in addition to pyruvate dehydrogenase complex and alpha-ketoglutarate dehydrogenase complex activity; no abnormality was found. Although the clinical features of thiamine-responsive congenital lactic acidosis are heterogeneous and clinical responses to thiamine administration vary, we emphasize the importance of early diagnosis and initiation of thiamine therapy before the occurrence of permanent brain damage. Careful monitoring of lactate and pyruvate would be useful in determining thiamine dosage.

Acidosis, Lactic↗
PubMed1988

Metabolic effects of partial reversal of pyruvate dehydrogenase activity by dichloroacetate in sepsis.

The metabolic effects of dichloroacetate on carbohydrate metabolism were investigated in normal fed, sterile inflammatory, and chronic septic animals. Chronic sepsis, but not sterile inflammation, was associated with elevated plasma, liver, and skeletal muscle lactate concentrations. Sodium dichloroacetate significantly reduced both plasma and intracellular pyruvate and lactate concentrations in all conditions examined, while plasma glucose concentrations remained unchanged. Decreased tissue metabolite concentrations were associated with a significantly increased active pyruvate dehydrogenase complex in liver and skeletal muscle in each of the conditions examined. In liver, dichloroacetate fully activated (greater than 85%) the pyruvate dehydrogenase complex under all conditions. In skeletal muscle from chronic septic animals, the dichloroacetate-induced increases in active pyruvate dehydrogenase were significantly less than those observed in non-septic animals. The data suggest that although dichloroacetate can partially reverse the sepsis-induced effects on skeletal muscle pyruvate dehydrogenase activity, there may be additional regulatory factors in skeletal muscle from septic animals. The dichloroacetate stimulation of the pyruvate dehydrogenase activity may provide a pharmacological method for reducing the elevated lactate concentrations observed in chronic severe sepsis.

Abscess↗
PubMedDate not supplied

[Effect of C-4'-modification of thiamine pyrophosphate on its coenzyme activity in the oxidative decarboxylation of pyruvic acid reaction].

Interaction was studied between pyruvate dehydrogenase (EC 1.2.4.1) and C-4'-substituted analogs of thiaminpyrophosphate, 4'-N (CH3)-TPP, 4'-N(CH3)2-TPP and OH-TPP. None of these analogs was found to replace TPP during the reduction of NAD and 2.6-dichlorophenol-indophenol as well as pyruvate decarboxylation. The decarboxylase activity of the pyruvate dehydrogenase component isolated from the pyruvate dehydrogenase complex was determined according to the 14CO2 yield and production of 2-C-oxoethyl-TPP using 1-14C-pyruvate and 2-14C-pyruvate, as substrates, respectively. All the analogs were found to competitively inhibit pyruvate dehydrogenase, Ki values for 4'-N(CH3)-TPP, 4'-N(CH3)2-TPP and 4'-OH-TPP being 4.1 X 10(-5) M, 8.5 X 10(-5) M and 2.9 X 10(-6) M, respectively; Km values for TPP was equal to 1-2 X 10(-7) M. It is assumed that the analogs of the holoenzymic complex formed by the pyruvate dehydrogenase component of the pyruvate dehydrogenase complex with mono-, dimethyl-TPP and oxo-TPP do not bind the substrate.

Animals↗