SEARCH · PubMed Health

Results for “Pyruvate dehydrogenase”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 433 records · Page 24Linked to original sources

PubMed1981

[Lag period as affected by the adrenal pyruvate dehydrogenase complex containing residual endogenous thiamine pyrophosphate].

The pyruvate dehydrogenase complex from bovine adrenals does not completely lose thiamine pyrophosphate (TPP) in the course of purification. The preparations contain firmly bound residual TPP in the amount providing for one third of the maximal activity of the complex. A lag period (tau) is observed during catalysis by the pyruvate dehydrogenase complex with the residual TPP in the absence of exogenous coenzyme. The duration of the lag period depends on concentration of the complex: tau is decreased as the concentration increases. The decrease of the lag period occurs after preincubation of the complex with pyruvate, but it is the most remarkable after preincubation with pyruvate and CoA. The tetrahydrothiamine pyrophosphate at low concentrations completely inhibits the activity. However, the residual TPP is retained as is evidenced by the recovery of the complex activity after gel-filtration through Sephadex G-25. The development of the lag period may be interpreted in terms of partial limited dissociation of the residual TPP in the region of the catalytic center.

Adrenal Glands↗

PubMed1986

Properties of a newly characterized protein of the bovine kidney pyruvate dehydrogenase complex.

The dihydrolipoyl transacetylase component, which serves as the structural core of mammalian pyruvate dehydrogenase complexes, is acetylated when treated with either pyruvate or with acetyl-CoA in the presence of NADH. Besides the dihydrolipoyl transacetylase component, we have found that another protein, referred to as protein X, is rapidly acetylated at thiol residues. Protein X remains fully bound to the transacetylase core under conditions that remove the pyruvate dehydrogenase and dihydrolipoyl dehydrogenase components. Mapping of 125I-tryptic peptides indicated that the transacetylase subunits and protein X are structurally distinct; however, under the same mapping conditions, there is considerable similarity in the positions of acetylated peptides derived from these subunits. Affinity-purified rabbit immunoglobulin G prepared against the dihydrolipoyl transacetylase core reacted exclusively with the transacetylase and with both its tryptic-derived inner domain and outer lipolyl-bearing domain. Those results further indicate that protein X is not derived from the transacetylase subunit Affinity-purified mouse antibody to protein X reacted selectively with large tryptic polypeptides derived from protein X and did not react with the inner domain of the transacetylase. However, the anti-protein X antibody did react with the intact transacetylase subunit, the lipoyl-bearing domain of the transacetylase, and weakly with the transsuccinylase component of the alpha-ketoglutarate dehydrogenase complex. This cross-reactivity reflected specificity of a portion of the polyclonal antibodies for a related structural region in the transacetylase and protein X (possibly a similar lipoyl-bearing region). Furthermore, a major portion of that polyclonal antibody was shown to react exclusively with protein X. Thus, protein X subunits differ substantially from transacetylase subunits but the two components have a region of structural similarity. We estimate that there are about 5 mol of protein X per mol of the kidney pyruvate dehydrogenase complex. Under a variety of conditions that result in a wide range of levels of acetylation of sites in the complex, about 1 acetyl group is incorporated into protein X per 10 acetyl groups incorporated into the transacetylase subunits per mol of complex. That ratio is close to the ratio of protein X subunits of transacetylase subunits in the complex, indicating that there are efficient mechanisms for acylation and deacylation of protein X.

Acetylation↗

PubMed1981

Regulatory properties of the pyruvate dehydrogenase complex of Pseudomonas aeruginosa.

The pyruvate dehydrogenase multienzyme complex of Pseudomonas aeruginosa was subjected to a steady-state kinetic analysis using the exponential model for a regulatory enzyme and a sensitive statistical fitting procedure. This showed that all the substrates, pyruvate, CoA and NAD+, exhibit cooperative kinetics towards the native multienzyme complex.

Coenzyme A↗

PubMed1984

Subunit binding in the pyruvate dehydrogenase complex from bovine kidney and heart.

Binding of pyruvate dehydrogenase (E1) and dihydrolipoamide dehydrogenase (E3) to the isolated dihydrolipoamide acetyltransferase (E2) core of the pyruvate dehydrogenase complex from bovine heart and kidney was investigated with equilibrium, competitive binding, and kinetic methods. E2, which consists of 60 subunits arranged with icosahedral 532 symmetry, apparently possesses six equivalent, noninteracting binding sites for E3 dimers. It is proposed that each E3 dimer extends across 2 of the 12 faces of the E2 pentagonal dodecahedron. The equilibrium constant (Kd) for dissociation of E3 from E2 is about 3 nM, and the dissociation rate constant is about 0.057 min-1. For E1, Kd is about 13 nM, and the dissociation rate constant is about 0.043 min-1. Extensive phosphorylation of E1 (about three phosphoryl groups per E1 tetramer) increases Kd to about 40 nM.

Acetyltransferases↗

PubMed2002

Regulation of pyruvate dehydrogenase (PDH) activity in human skeletal muscle during exercise.

Pyruvate dehydrogenase is a mitochondrial multienzyme complex that catalyzes the conversion of pyruvate to acetyl-coenzyme A and regulates the entry of carbohydrate into the tricarboxylic acid cycle for oxidation. During exercise, pyruvate dehydrogenase activation in human skeletal muscle is proportional to the relative aerobic power output (percent VO2max) and is regulated by increases in Ca2+, free ADP, and pyruvate concentrations.

Acetyl Coenzyme A↗

PubMed2004

Manipulating the pyruvate dehydrogenase bypass of a multi-vitamin auxotrophic yeast Torulopsis glabrata enhanced pyruvate production.

AIMS: To investigate the relationship between the activity of pyruvate dehydrogenase (PDH) bypass and the production of pyruvate of a multi-vitamin auxotrophic yeast Torulopsis glabrata. METHODS AND RESULTS: Torulopsis glabrata CCTCC M202019, a multi-vitamin auxotrophic yeast that requires acetate for complete growth on glucose minimum medium, was selected after nitrosoguanidine mutagenesis of the parent strain T. glabrata WSH-IP303 screened in previous study [Li et al. (2001) Appl. Microbiol. Biotechnol. 55, 680-685]. Strain CCTCC M202019 produced 21% higher pyruvate than the parent strain and was genetically stable in flask cultures. The activities of the pyruvate metabolism-related enzymes in parent and mutant strains were measured. Compared with the parent strain, the activity of pyruvate decarboxylase (PDC) of the mutant strain CCTCC M202019 decreased by roughly 40%, while the activity of acetyl-CoA synthetase (ACS) of the mutant increased by 103.5 or 57.4%, respectively, in the presence or absence of acetate. Pyruvate production by the mutant strain CCTCC M202019 reached 68.7 g l(-1) at 62 h (yield on glucose of 0.651 g g(-1)) in a 7-l jar fermentor. CONCLUSIONS: The increased pyruvate yield in T. glabrata CCTCC M202019 was due to a balanced manipulation of the PDH bypass, where the shortage of cytoplasmic acetyl-CoA caused by the decreased activity of PDC was properly compensated by the increased activity of ACS. SIGNIFICANCE AND IMPACT OF THE STUDY: Manipulating the PDH bypass may provide an alternative approach to enhance the production of glycolysis-related metabolites.

Acetates↗

PubMed1986

Lipoic acid is the site of substrate-dependent acetylation of component X in ox heart pyruvate dehydrogenase multienzyme complex.

The recently characterized Mr-50000 polypeptide associated with mammalian pyruvate dehydrogenase complex, referred to as component or protein X, was shown to incorporate N-ethylmaleimide only in the presence of pyruvate or NADH. Component X, modified with N-ethyl[2,3-14C]maleimide in the presence of pyruvate, was isolated and subjected to acid hydrolysis. The radioactive products were resolved on an amino acid analyser and these coeluted with products from similarly modified and hydrolysed lipoate acetyltransferase. Preincubation of pyruvate dehydrogenase complex with pyruvate or NADH and acetyl-CoA resulted in a time-dependent diminution of incorporation of radiolabelled N-ethylmaleimide into component X and lipoate acetyltransferase and, correspondingly, in the extent of inhibition of overall complex activity by N-ethylmaleimide.

Acetylation↗

PubMed1985

Pyruvate dehydrogenase complex from ribbed mussel gill mitochondria.

The pyruvate dehydrogenase complex has been demonstrated in high speed pellet preparations from sonicated ribbed mussel gill mitochondria. The activity of the complex is inhibited by low chloride (less than 100 mM) concentrations, EDTA (1 mM), succinate, ATP, and NAD/NADH ratios below 4. Inhibition by EDTA is relieved by addition of 10 mM MgCl2-1 mM CaCl2. ATP inhibition was enhanced by NaF and reversed by high Mg++ concentrations in the absence of NaF. Pyruvate and thiamine pyrophosphate inhibited the inactivation by ATP. The nonhydrolyzable ATP analog AMP-PNP caused inhibition of the overall catalytic activity that was identical to ATP. Factors involved in the ATP inhibition and Mg++ reversal are lost with freezing or cold storage. Preliminary results using gamma-32P-ATP indicate that a protein kinase that phosphorylates the alpha subunit of E1 (pyruvate dehydrogenase) from the mammalian PDC is associated with the gill PDC. The activity of the complex may be regulated by a phosphorylation/dephosphorylation mechanism and by the relative levels of substrates, products, and other metabolites in the mitochondria.

Animals↗

PubMed1990

Defects in the E2 lipoyl transacetylase and the X-lipoyl containing component of the pyruvate dehydrogenase complex in patients with lactic acidemia.

Three patients with chronic lacticacidemia and deficiency of the pyruvate dehydrogenase complex demonstrated in cultured skin fibroblasts showed abnormalities on Western blotting with anti-pyruvate dehydrogenase complex antiserum which were not located in the E1 (alpha and beta) component of the complex. One of these patients had an enzymatically demonstrable deficiency in the E2 dihydrolipoyl transacetylase segment of the complex and very low observable E2 protein component on Western blotting of fibroblast proteins. The other two patients had abnormalities observable in the X component but no observable reduction in either E1, E2, or E3 enzymatic activities. One patient appeared to have a missing X component while the other had two distinct bands where X should be on Western blotting of fibroblast proteins. All three patients appeared to have severe clinical sequelae resulting from these defects. This is the first time that defects in either the E2 or the X component of the pyruvate dehydrogenase complex have been observed in the human population.

Acetyltransferases↗

PubMed2006

Pyruvate dehydrogenase phosphatase deficiency: orphan disease or an under-diagnosed condition?

Pyruvate dehydrogenase phosphatase (PDP) is an enzyme which regulates the activity of the pyruvate dehydrogenase complex (PDHc). In the past, PDHc deficiency has been attributed to mutations in the complex itself and the regulatory enzymes have not been considered. We have recently reported the first mutation in PDP1, one of the two isoforms of PDP, which results in severe exercise intolerance and mild developmental delay in patients. This novel process of aberrant pyruvate metabolism opens up a new avenue for investigation into PDHc deficiency, that has hitherto been underappreciated.

Humans↗

PubMed1993

Formation of N-hydroxy-N-arylacetamides from nitroso aromatic compounds by the mammalian pyruvate dehydrogenase complex.

Bovine, human and porcine heart mitochondria and isolated porcine heart pyruvate dehydrogenase complex (PDHC) pyruvate-dependently form N-hydroxy-N-arylacetamides from nitroso aromatic compounds, including carcinogenic 4-biphenyl and 2-fluorenyl derivatives. The PDHC-catalysed formation of N-hydroxyacetanilide (N-OH-AA) from nitrosobenzene (NOB), through a Ping Pong mechanism, is optimum at pH 6.8 and is accelerated by thiamin pyrophosphate, but is inhibited by thiamin thiazolone pyrophosphate and ATP. Km pyruvate in the reaction is independent of pH over the range tested, whereas KmNOB increases at lower pH, owing to ionization of an active-site functional group of pKa 6.3. The enzymic ionization decreases log (Vmax/KmNOB). Isolated pyruvate dehydrogenase (E1), a constitutive enzyme of PDHC, forms N-OH-AA by itself and has comparable kinetic parameters to those of the PDHC-catalysed N-OH-AA formation. The catalytic efficiency of PDHC in the formation of N-hydroxy-N-arylacylamides, due to the steric limitation of the active site of E1, is lowered both by bulky alkyl groups of alpha-oxo acids and by p-substituents (but not an o-substituent) on nitrosobenzenes. These nitroso compounds serve as electrophiles in the reaction in which the reductive acetylation step is rate-limiting. The reaction mechanism and other factors affecting N-hydroxy-N-arylacylamide formation are discussed.

Acetamides↗

PubMed2006

A novel gross deletion caused by non-homologous recombination of the PDHX gene in a patient with pyruvate dehydrogenase deficiency.

We report here the molecular analysis of a pyruvate dehydrogenase E3-binding protein (PDH-E3BP) deficiency in a new patient, born to first cousin parents. She has initially presented with a non-progressive and unspecific encephalopathy, followed by an acute neurological deterioration at 14 years of age. E3BP subunit was undetectable on Western blot. The sequence of exons 1-9 and exon 11 of the PDHX gene were normal, but exon 10 was impossible to amplify with standard PCR. Long-range PCR including exons 9-11 (11.5 kb) was performed. The patient's sample displayed a unique PCR product of 7.5 kb, whereas the parents' samples displayed two bands (11.5 and 7.5 kb). The deletion breakpoints were determined by restriction analysis followed by direct sequencing. The homozygous deletion covered the end of intron 9, exon 10 and the beginning of intron 10 and was found to be 3913 bp long. The cDNA sequencing confirmed the deletion of exon 10. The most probable mechanism for this gross deletion appears to be a slipped mispairing mediated by an exact direct repeat CCACTG. It is the first time that a non-homologous recombination is reported in the PDHX gene causing pyruvate dehydrogenase complex (PDHc) deficiency.

Adolescent↗

PubMed2005

Role of protein-protein interactions in the regulation of pyruvate dehydrogenase kinase activity.

The transacetylase component (E2) of PDC (pyruvate dehydrogenase complex) plays a critical role in the regulation of PDHK (pyruvate dehydrogenase kinase) activity. The present study was undertaken to investigate further the molecular mechanism by which E2 modulates the activity of PDHK. In agreement with the earlier results, it was found that the inner L2 (lipoyl-bearing domain 2) of E2 expressed with or without the C-terminal hinge region had little, if any, effect on the kinase activity, indicating a lack of direct allosteric effect of L2 on PDHK. In marked contrast, significant activation of PDHK was observed with the construct consisting of L2 and the E1BD (E1-binding domain) of E2 (L2-E1BD didomain) suggesting that co-localization and/or mutual orientation of PDHK and E1, facilitated by E2 binding, largely account for the activation of PDHK by the transacetylase component. Isothermal titration calorimetry and glutathione S-transferase pull-down assays established that binding of adenyl nucleotides to the PDHK molecule facilitated the release of L2 domain. In contrast, binding of the L2 domain caused a significant decrease in the affinity of PDHK for ATP. The cross-talk in binding of adenyl nucleotides and the L2 domain to PDHK may indicate the existence of a highly integrated mechanism whereby the exchange of lipoyl-bearing domains presented to PDHK by E2 is coupled with ADP/ATP exchange.

Acetyltransferases↗

PubMed1988

Phosphorylation and inactivation of the pyruvate dehydrogenase from the anaerobic parasitic nematode, Ascaris suum. Stoichiometry and amino acid sequence around the phosphorylation sites.

Tryptic digestion of the fully phosphorylated Ascaris suum pyruvate dehydrogenase complex yielded a single tetradecapeptide containing 2 phosphorylated serine residues. Its amino acid sequence was Tyr-Ser-Gly-His-Ser(P)-Met-Ser-Asp-Pro-Gly-Thr-Ser(P)-Tyr-Arg and was very similar to one of the tryptic phosphopeptides isolated from mammalian and yeast pyruvate dehydrogenases. At partial phosphorylation, three peptides were isolated which corresponded to the monophosphorylated (sites 1 and 2) and diphosphorylated tetradecapeptides. In contrast to results reported from mammalian complexes, phosphorylation of the ascarid complex paralleled inactivation, and no additional phosphorylation occurred after inactivation was complete. Complete inactivation of the complex was associated with the incorporation of 1.7-1.9 mol of phosphoryl groups/mol of alpha-pyruvate dehydrogenase subunit, and the strict preference of the pyruvate dehydrogenase kinase for site 1 was not observed. Whereas site 1 was initially phosphorylated more rapidly than site 2, at 50% inactivation, 41% of the incorporated phosphoryl groups were incorporated into site 2. In addition, substantial amounts of peptide monophosphorylated at site 2 also accumulated, suggesting that prior phosphorylation at site 1 was not necessary for phosphorylation at site 2. Phosphorylation also caused a marked decrease in the mobility of the alpha-pyruvate dehydrogenase subunit on sodium dodecyl sulfate-polyacrylamide gels and the apparent separation of mono- and diphosphorylated forms of the enzyme. The significance of these observations in the regulation of the unique anaerobic mitochondrial metabolism of A. suum is discussed.

Amino Acid Sequence↗

PubMed1994

Enzyme-linked immunosorbent assays for the determination of IgG, IgA, and IgM autoantibodies to pyruvate dehydrogenase in primary biliary cirrhosis.

Autoantibodies to the recently described mitochondrial autoantigen, pyruvate dehydrogenase, have been shown to be specific for primary biliary cirrhosis. In the present study we describe enzyme-linked immunosorbent assays to detect antibodies of IgG, IgA, and IgM classes reactive with pyruvate dehydrogenase. These assays showed high sensitivity (95%) and specificity (100%) for primary biliary cirrhosis when evaluated in 28 patients with primary biliary cirrhosis, 59 disease controls, and 214 healthy persons. Quantitation of these autoantibodies by calculating the areas under the sera titration curves of 10 primary biliary cirrhosis patients indicated that an increase in IgA antibodies to pyruvate dehydrogenase is related to more rapid disease progression.

Autoantibodies↗

PubMed1999

Cerebral palsy and pyruvate dehydrogenase deficiency: identification of two new mutations in the E1alpha gene.

UNLABELLED: Pyruvate dehydrogenase (PDH) complex deficiency, a common cause of congenital lactic acidosis, is mostly due to mutations in the X-linked gene coding for the E1alpha subunit of the complex. We have studied two unrelated girls presenting a static encephalopathy with spastic quadriplegia, microcephaly and seizures and in one girl, hypocalcaemia, a new finding in PDH complex deficiency. PDH deficiency was diagnosed in adolescence and both girls had low PDH complex activity in muscle but normal amounts of all subunits on Western blotting, and a normal lactate/pyruvate ratio in blood and CSF. Mutation analysis of the E1alpha gene at the cDNA or DNA level revealed an arginine to histidine substitution at amino acid position 288 (R288H) in the girl with hypocalcaemia and a 12 bp insertion, predicting a four amino acid duplication at the c-terminal end of the protein in the second girl. They both carried a normal and a mutated E1alpha gene and X-inactivation studies showed skewed patterns. CONCLUSION: Mutation identification in pyruvate dehydrogenase complex deficiency remains important especially for the determination of the recurrence risk and for reliable genetic counselling in couples with an affected child.

Acidosis, Lactic↗

PubMed1980

Studies on the incorporation of [32P]phosphate into pyruvate dehydrogenase in intact rat fat-cells. Effects of insulin.

1. Intact rat epididymal fat-cells were incubated with 32Pi, and the intracellular proteins were separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. One of the separated bands of phosphorylated proteins had an apparent subunit mol.wt. of 42 000, which is the same as that of the alpha-subunit of the pyruvate dehydrogenase complex. By using a combination of subcellular fractionation, immunoprecipitation with antiserum raised against pyruvate dehydrogenase complex and two-dimensional electrophoresis it was apparent that the incorporation into alpha-subunits accounted for 35--45% of the total incorporation into this band of phosphoproteins. 2. The increase in the initial activity of pyruvate dehydrogenase that follows brief exposure of fat-cells to insulin was shown to be associated with a decrease in the steady-state incorporation of 32P into the alpha-subunits of pyruvate dehydrogenase. 3. Tryptic peptide analysis of pyruvate dehydrogenase [32P]phosphate, labelled in intact fat-cells, indicated that three serine residues on the alpha-subunit were phosphorylated, corresponding to the three sites phosphorylated when purified pig heart pyruvate dehydrogenase was incubated with [gamma-32P]ATP. The relative phosphorylation of all three serine residues appeared to be similar in 32P-labelled alpha-subunits in both control and insulin-treated fat-cells.

Adipose Tissue↗

PubMed1977

Structure of pyruvate dehydrogenase complex. Comparison between freeze-etching and negative staining.

Pyruvate dehydrogenase complex (pyruvate : lipoate oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1), from pig heart, was studied by spray freeze etching and negative staining. From freeze etching experiments an average particle weight of 7-10(6) was estimated. Negative staining after glutaraldehyde fixation and freeze etching of unfixed and prefixed enzyme solutions yielded no significant difference in particle dimensions: the majority of the isometric complex molecules measured approximately 400 A in diameter. Tantalum tungsten shadowed freeze etch replicas indicated that the surface of the complex is built up of globular units. The relative positions of these units are in good agreement with the model still under discussion.

Animals↗