PubMed Health⌕ Search

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 199 records · Page 11Linked to original sources
PubMed1984

Age-related changes in liver and adipose tissue pyruvate dehydrogenase of genetically obese mice.

Changes of the pyruvate dehydrogenase complex in liver and epididymal fat pad were examined longitudinally in obese mice (C57BL/6J-ob/ob) and their lean controls as a function of age. Total pyruvate dehydrogenase in liver was expressed on several reference bases because of differences in hepatic cellularity and protein content between obese mice and their age-matched lean controls. When total hepatic pyruvate dehydrogenase was expressed on a protein basis, the enzyme activity was elevated in obese mice older than 28 weeks in age when compared to lean controls of a similar age. However, when expressed on a DNA basis, total pyruvate dehydrogenase activity in livers of obese mice up to 10 weeks in age was increased when compared to the age-matched lean control. The proportion of hepatic pyruvate dehydrogenase in the active form was also augmented significantly in obese mice from 5 to 28 weeks of age. In 18-week-old obese mice, the proportion of total pyruvate dehydrogenase in the active form of adipose tissue was significantly higher than that of the lean controls. When expressed on a DNA basis, total pyruvate dehydrogenase in the fat pad was also increased in obese mice up to 10 weeks in age when compared to age-matched controls. Total pyruvate dehydrogenase activity in the epididymal fat pad was higher in obese mice than the lean controls in animals as old as 32 weeks in age when the enzyme activity was expressed per 100 g body weight. The increase in the active form and total activity of pyruvate dehydrogenase in both liver and epididymal fat pad during the dynamic early phase of obesity would augment the capacity for acetyl-coenzyme A formation necessary in the support of an accelerated lipogenesis and fat deposition.

Adipose Tissue↗
PubMed1986

Characterization and immunochemistry of pyruvate dehydrogenase complex of Ascaris muscle.

Pyruvate dehydrogenase complex and lipoamide dehydrogenase were purified from muscle of Ascaris lumbricoides var. suum which contains relatively a large amount of the complex. Molecular weights of three constituent enzymes of Ascaris pyruvate dehydrogenase complex were as follows; alpha- and beta-subunits of pyruvate dehydrogenase were 42,000 and 37,000, respectively, lipoate acetyltransferase was 76,000 and lipoamide dehydrogenase was 56,000. Furthermore, two unknown polypeptides having molecular weight of 46,000 and 41,000 were detected. Anti-Ascaris lipoamide dehydrogenase antibody precipitated three constituent enzymes and two unknown polypeptides, suggesting that lipoamide dehydrogenase not only binds tightly to complex, but also two unknown polypeptides bind tightly to complex.

Animals↗
PubMed1990

Involvement of pyruvate dehydrogenase in product formation in pyruvate-limited anaerobic chemostat cultures of Enterococcus faecalis NCTC 775.

Enterococcus faecalis NCTC 775 was grown anaerobically in chemostat culture with pyruvate as the energy source. At low culture pH values, high in vivo and in vitro activities were found for both pyruvate dehydrogenase and lactate dehydrogenase. At high culture pH values the carbon flux was shifted towards pyruvate formate lyase. Some mechanisms possibly involved in this metabolic switch are discussed. In particular attention is paid to the NADH/NAD ratio (redox potential) and the fructose-1,6-bisphosphate-dependent lactate dehydrogenase activity as possible regulatory factors.

Acetyltransferases↗
PubMed1983

Induction of pyruvate dehydrogenase in 3T3-L1 cells during differentiation.

The activity of the pyruvate dehydrogenase complex and the content and turnover of the pyruvate dehydrogenase component were measured during the differentiation of 3T3-L1 preadipocytes into 3T3-L1 adipocytes. The specific activity of "total" pyruvate dehydrogenase complex increased approximately 7-fold in 3T3-L1 adipocytes differentiated with a treatment of insulin plus dexamethasone plus 1-methyl-3-isobutyl xanthine. The ratio of "active" pyruvate dehydrogenase complex to total pyruvate dehydrogenase complex remained unaltered in both 3T3-L1 preadipocytes and adipocytes. A specific goat antibody to bovine kidney pyruvate dehydrogenase quantitatively precipitated both alpha and beta subunits of pyruvate dehydrogenase from solubilized 3T3-L1 adipocytes. Using immunoprecipitation and gel electrophoresis techniques, we demonstrated an approximate 6-fold increase in pyruvate dehydrogenase content in 3T3-L1 adipocytes as compared to 3T3-L1 preadipocytes. Pulse labeling experiments revealed an approximately 5-fold increase in the rates of synthesis of both alpha and beta subunits of pyruvate dehydrogenase in 3T3-L1 adipocytes after 6 days of the hormonal treatment compared to those observed in 3T3-L1 preadipocytes. In contrast, the half-lives of alpha and beta subunits of pyruvate dehydrogenase were not significantly altered in 3T3-L1 preadipocytes (41 h) and adipocytes (49 h). The 6-8-fold increment in the specific activity of the pyruvate dehydrogenase complex in 3T3-L1 adipocytes therefore results from increased rates of synthesis of alpha and beta subunits of pyruvate dehydrogenase.

Adipose Tissue↗
PubMed1991

Characterization of cDNA clones for the beta subunit of pyruvate dehydrogenase from Ascaris suum.

The pyruvate dehydrogenase complex occupies a unique position in the anaerobic mitochondrial metabolism of the parasitic nematode Ascaris suum. This paper describes cDNA clones for the beta subunit of the pyruvate dehydrogenase component of this complex. A cDNA library has been constructed in lambda gt11 from poly(A)+ RNA isolated from adult ascarid body wall muscle. The library was screened with antiserum prepared against the beta subunit of pyruvate dehydrogenase. Full-length clones of 1.2 kb have been characterized. The first 15 amino acids determined from the purified protein match exactly those predicted from the cDNA sequence. The deduced protein sequence contains a 26-amino-acid presequence that has characteristics of mitochondrial targeting sequences. The mature protein is predicted to contain 334 amino acids and is 62% identical to the predicted sequence of the corresponding human subunit. Full-length in vitro transcripts have been translated in vitro to yield a 39-kDa polypeptide consistent with the open reading frame present in the cDNA sequence. The 90 nucleotides at the 3' end of the cDNA sequence have the potential to form a cruciform structure that may play a role in the synthesis of the enzyme.

Amino Acid Sequence↗
PubMed2003

Recent advances in mechanisms regulating glucose oxidation at the level of the pyruvate dehydrogenase complex by PDKs.

The mitochondrial pyruvate dehydrogenase complex (PDC) catalyzes the oxidative decarboxylation of pyruvate, linking glycolysis to the tricarboxylic acid cycle and fatty acid (FA) synthesis. Knowledge of the mechanisms that regulate PDC activity is important, because PDC inactivation is crucial for glucose conservation when glucose is scarce, whereas adequate PDC activity is required to allow both ATP and FA production from glucose. The mechanisms that control mammalian PDC activity include its phosphorylation (inactivation) by a family of pyruvate dehydrogenase kinases (PDKs 1-4) and its dephosphorylation (activation, reactivation) by the pyruvate dehydrogenase phosphate phosphatases (PDPs 1 and 2). Isoform-specific differences in kinetic parameters, regulation, and phosphorylation site specificity of the PDKs introduce variations in the regulation of PDC activity in differing endocrine and metabolic states. In this review, we summarize recent significant advances in our knowledge of the mechanisms regulating PDC with emphasis on the PDKs, in particular PDK4, whose expression is linked with sustained changes in tissue lipid handling and which may represent an attractive target for pharmacological interventions aimed at modulating whole body glucose, lipid, and lactate homeostasis in disease states.

Animals↗
PubMed1984

Stimulation of pyruvate dehydrogenase phosphatase activity by polyamines.

Pyruvate dehydrogenase phosphatase requires Mg2+ or Mn2+, and its activity in the presence of Mg2+ is markedly stimulated by Ca2+. At saturating Mg2+ and Ca2+ concentrations, the polyamines spermine, spermidine and putrescine stimulated the activity of pyruvate dehydrogenase phosphatase 1.5- to 3-fold. Spermine was the most active of the polyamines. At a physiological concentration of Mg2+ (1 mM) and saturating Ca2+ concentration, the stimulation by 0.5 mM spermine was 4- to 5-fold, and at 0.3 mM Mg2+, the stimulation was 20- to 30-fold. In the absence of Mg2+ or Ca2+, spermine had no effect. These results suggest that a polybasic factor may be involved in the regulation of pyruvate dehydrogenase phosphatase activity.

Animals↗
PubMed1994

Molecular cloning of the p45 subunit of pyruvate dehydrogenase kinase.

Purified preparations of rat heart pyruvate dehydrogenase kinase have two polypeptides with molecular weights of 48,000 (p48) and 45,000 (p45). Recently, we reported the primary structure of p48 (Popov, K. M., Kedishvili, N. Y., Zhao, Y., Shimomura, Y., Crabb, D. W., and Harris, R. A. (1993) J. Biol. Chem. 268, 26602-26606) and presented evidence that (i) it exhibits kinase activity for pyruvate dehydrogenase and (ii) it belongs to a family of mitochondrial protein kinases unique from other eukaryotic protein kinases. Here, we report the molecular cloning and deduced amino acid sequence of p45. The protein sequence of p45 has 70% identity to the protein sequence of p48. Minor differences exist throughout the protein sequences with the greatest difference occurring at the amino termini. Recombinant p45 protein, expressed in Escherichia coli and purified to homogeneity, catalyzed the phosphorylation and inactivation of kinase-depleted pyruvate dehydrogenase complex, indicating that p45 and p48 correspond to different isoforms of pyruvate dehydrogenase kinase. Northern blot analysis revealed a single hybridizing species of 2.5 kilobases. The highest level of p45 message expression was found in heart and skeletal muscle and the lowest in spleen and lung. Liver, kidney, brain, and testis express intermediate amounts of p45 mRNA. In contrast, p48 mRNA is predominantly expressed in heart, with other tissues expressing only a modest amount of this message. Tissue-specific expression of isoforms of pyruvate dehydrogenase kinase may indicate the existence of tissue-specific mechanisms for the regulation of pyruvate dehydrogenase activity.

Amino Acid Sequence↗
PubMed1976

Studies on the formation of acetoin from acetaldehyde by the pyruvate dehydrogenase complex and its regulation.

1. Pyruvate dehydrogenase complex was isolated from pigeon breast muscle involving steps of isoelectric precipitation, poly(ethyleneglycol) fractionation and separation on a glycerine gradient in the ultracentrifuge. 2. Arsenite, a potent inhibitor of the dihydrolipoyl transcetylase, did not affect the formation of acetoin from acetaldehyde, indicating that the pyruvate dehydrogenase component was operative in this reaction. 3. Production of acetoin by the pyruvate dehydrogenase complex is subject to regulation by phosphorylation and dephosphorylation, the dephosphorylated form only being active. 4. The inhibition by acetaldehyde of the pyruvate dehydrogenase complex could be partly explained by the formation of acetoin as an alternative reaction.

Acetaldehyde↗
PubMed1992

Characterization of cDNA clones for the alpha subunit of pyruvate dehydrogenase from Ascaris suum.

The pyruvate dehydrogenase complex of the adult parasitic nematode Ascaris suum functions in the reducing environment present in their anaerobic mitochondria. These organelles use fumarate and enoyl CoAs as terminal electron acceptors instead of oxygen. A lambda gt11 cDNA library was constructed from RNA isolated from adult ascarid muscle. Partial clones for the pyruvate dehydrogenase alpha subunit were isolated by screening the lambda gt11 library with a specific antiserum. Full-length clones (type I) were identified in a cDNA library prepared from RNA isolated from early embryos. During the hybridization screening, a second type of cDNA clone (type II) was identified. The nucleotide sequences of both clones are presented. The predicted amino acid sequences of the mature proteins are 91% identical to one another and about 55% identical to the predicted sequences of the alpha subunit of human pyruvate dehydrogenase. Northern blots were used to examine the expression of both mRNAs in various larval stages and in tissues of the adult. Type I sequences are found mainly in adult muscle. Type II sequences are abundant in third-stage larvae as well as in adult muscle.

Amino Acid Sequence↗
PubMed2001

Distinct regulatory properties of pyruvate dehydrogenase kinase and phosphatase isoforms.

The mammalian pyruvate dehydrogenase complex (PDC) plays central and strategic roles in the control of the use of glucose-linked substrates as sources of oxidative energy or as precursors in the biosynthesis of fatty acids. The activity of this mitochondrial complex is regulated by the continuous operation of competing pyruvate dehydrogenase kinase (PDK) and pyruvate dehydrogenase phosphatase (PDP) reactions. The resulting interconversion cycle determines the fraction of active (nonphosphorylated) pyruvate dehydrogenase (E1) component. Tissue-specific and metabolic state-specific control is achieved by the selective expression and distinct regulatory properties of at least four PDK isozymes and two PDP isozymes. The PDK isoforms are members of a family of serine kinases that are not structurally related to cytoplasmic Ser/Thr/Tyr kinases. The catalytic subunits of the PDP isoforms are Mg2+-dependent members of the phosphatase 2C family that has binuclear metal-binding sites within the active site. The dihydrolipoyl acetyltransferase (E2) and the dihydrolipoyl dehydrogenase-binding protein (E3BP) are multidomain proteins that form the oligomeric core of the complex. One or more of their three lipoyl domains (two in E2) selectively bind each PDK and PDP1. These adaptive interactions predominantly influence the catalytic efficiencies and effector control of these regulatory enzymes. When fatty acids are the preferred source of acetyl-CoA and NADH, feedback inactivation of PDC is accomplished by the activity of certain kinase isoforms being stimulated upon preferentially binding a lipoyl domain containing a reductively acetylated lipoyl group. PDC activity is increased in Ca2+-sensitive tissues by elevating PDP1 activity via the Ca2+-dependent binding of PDP1 to a lipoyl domain of E2. During starvation, the irrecoverable loss of glucose carbons is restricted by minimizing PDC activity due to high kinase activity that results from the overexpression of specific kinase isoforms. Overexpression of the same PDK isoforms deleteriously hinders glucose consumption in unregulated diabetes.

Amino Acid Sequence↗
PubMed1979

Pyruvate Dehydrogenase Complex from Chloroplasts of Pisum sativum L.

Pyruvate dehydrogenase complex is associated with intact chloroplasts and mitochondria of 9-day-old Pisum sativum L. seedlings. The ratio of the mitochondrial complex to the chloroplast complex activities is about 3 to 1. Maximal rates observed for chloroplast pyruvate dehydrogenase complex activity ranged from 6 to 9 micromoles of NADH produced per milligram of chlorophyll per hour. Osmotic rupture of pea chloroplasts released 88% of the complex activity, indicating that chloroplast pyruvate dehydrogenase complex is a stromal complex. The pH optimum for chloroplast pyruvate dehydrogenase complex was between 7.8 and 8.2, whereas the mitochondrial pyruvate dehydrogenase complex had a pH optimum between 7.3 and 7.7. Chloroplast pyruvate dehydrogenase complex activity was specific for pyruvate, dependent upon coenzyme A and NAD and partially dependent upon Mg(2+) and thiamine pyrophosphate.Chloroplast-associated pyruvate dehydrogenase complex provides a direct link between pyruvate metabolism and chloroplast fatty acid biosynthesis by providing the substrate, acetyl-CoA, necessary for membrane development in young plants.

Journal Article↗
PubMed1999

Effects of antisense repression of an Arabidopsis thaliana pyruvate dehydrogenase kinase cDNA on plant development.

Pyruvate dehydrogenase kinase (PDHK), a negative regulator of the mitochondrial pyruvate dehydrogenase (PDH) complex (mtPDC), plays a pivotal role in controlling mtPDC activity, and hence, the TCA cycle and cell respiration. This report describes the cloning of a pyruvate dehydrogenase kinase cDNA (AtPDHK) from Arabidopsis thaliana and focuses on the effects of antisense down-regulation of its expression on plant growth and development. The deduced amino acid sequence of AtPDHK exhibits extensive similarity to other plant and mammalian PDHKs, containing conserved domains typical of two-component histidine protein kinases. The Escherichia coli expressed AtPDHK specifically phosphorylated mammalian PDH E1 in a time-dependent manner. Antisense expression of the AtPDHK cDNA led to marked elevation of mtPDC activity in transgenic plants with increases ranging from 137% to 330% compared to control plants. Immunoblot analyses performed with a monoclonal antibody to the E1alpha mtPDH component (the subunit phosphorylated by PDHK) indicated that the increased mtPDC activity was not the result of an increase in the level of PDH protein. MtPDC from transgenic plants showed a reduced sensitivity to ATP-dependent inactivation compared to that observed in wild-type plants. Collectively, these data suggest that the antisense partial silencing of the negative regulator, PDHK, was responsible for the increased mtPDC activity observed in the antisense PDHK plants. Transgenic plants with partially repressed AtPDHK also displayed altered vegetative growth with reduced accumulation of vegetative tissues, early flower development and shorter generation time. The potential role for AtPDHK gene manipulation in crop improvement is discussed.

Arabidopsis↗
PubMed1987

Some kinetic and regulatory properties of the pea mitochondrial pyruvate dehydrogenase complex.

The pyruvate dehydrogenase complex was isolated, partially purified, and characterized from green pea (Pisum sativum L., cv Little Marvel) leaf mitochondria. The pH optimum for the overall reaction was 7.6. The divalent cation requirement was best satisfied by Mg(2+). Reaction velocity was maximal at 40 degrees C. Pyruvate was a better substrate than 2-oxo-butyrate; other 2-oxo-acids were not substrates. Michaelis constants for substrates were; pyruvate, 57 micromolar; NAD, 122 micromolar; Coenzyme-A, 5 micromolar; Mg(2+), 0.36 millimolar; Mg-thiamine pyrophosphate, 80 nanomolar. The products, NADH and acetyl-Coenzyme-A, were linear competitive inhibitors with respect to NAD and Coenzyme A. Inhibition constants were 18 and 10 micromolar, respectively. Glyoxylate inhibited complex activity only in the absence of thiol reagents. Glyoxylate inhibition was competitive with respect to pyruvate with an inhibition constant of 51 micromolar. Among mitochondrial metabolites examined as potential effectors, only ADP with an inhibition constant of 0.57 millimolar could be of physiological significance.

Journal Article↗
PubMed1976

The elementary reactions of the pig heart pyruvate dehydrogenase complex. A study of the inhibition by phosphorylation.

1. A method was devised for preparing pig heart pyruvate dehydrogenase free of thiamin pyrophosphate (TPP), permitting studies of the binding of [35S]TPP to pyruvate dehydrogenase and pyruvate dehydrogenase phosphate. The Kd of TPP for pyruvate dehydrogenase was in the range 6.2-8.2 muM, whereas that for pyruvate dehydrogenase phosphate was approximately 15 muM; both forms of the complex contained about the same total number of binding sites (500 pmol/unit of enzyme). EDTA completely inhibited binding of TPP; sodium pyrophosphate, adenylyl imidodiphosphate and GTP, which are inhibitors (competitive with TPP) of the overall pyruvate dehydrogenase reaction, did not appreciably affect TPP binding. 2. Initial-velocity patterns of the overall pyruvate dehydrogenase reaction obtained with varying TPP, CoA and NAD+ concentrations at a fixed pyruvate concentration were consistent with a sequential three-site Ping Pong mechanism; in the presence of oxaloacetate and citrate synthase to remove acetyl-CoA (an inhibitor of the overall reaction) the values of Km for NAD+ and CoA were 53+/- 5 muM and 1.9+/-0.2 muM respectively. Initial-velocity patterns observed with varying TPP concentrations at various fixed concentrations of pyruvate were indicative of either a compulsory order of addition of substrates to form a ternary complex (pyruvate-Enz-TPP) or a random-sequence mechanism in which interconversion of ternary intermediates is rate-limiting; values of Km for pyruvate and TPP were 25+/-4 muM and 50+/-10 nM respectively. The Kia-TPP (the dissociation constant for Enz-TPP complex calculated from kinetic plots) was close to the value of Kd-TPP (determined by direct binding studies). 3. Inhibition of the overall pyruvate dehydrogenase reaction by pyrophosphate was mixed non-competitive versus pyruvate and competitive versus TPP; however, pyrophosphate did not alter the calculated value for Kia-TPP, consistent with the lack of effect of pyrophosphate on the Kd for TPP. 4. Pyruvate dehydrogenase catalysed a TPP-dependent production of 14CO2 from [1-14C]pyruvate in the absence of NAD+ and CoA at approximately 0.35% of the overall reaction rate; this was substantially inhibited by phosphorylation of the enzyme both in the presence and absence of acetaldehyde (which stimulates the rate of 14CO2 production two- or three-fold). 5. Pyruvate dehydrogenase catalysed a partial back-reaction in the presence of TPP, acetyl-CoA and NADH. The Km for TPP was 4.1+/-0.5 muM. The partial back-reaction was stimulated by acetaldehyde, inhibited by pyrophosphate and abolished by phosphorylation. 6. Formation of enzyme-bound [14C]acetylhydrolipoate from [3-14C]pyruvate but not from [1-14C]acetyl-CoA was inhibited by phosphorylation. Phosphorylation also substantially inhibited the transfer of [14C]acetyl groups from enzyme-bound [14C]acetylhydrolipoate to TPP in the presence of NADH. 7...

Acetaldehyde↗
PubMed1994

Leigh syndrome: pyruvate dehydrogenase defect. A case with peripheral neuropathy.

Pyruvate dehydrogenase deficiency is one of the most common causes of encephalopathy associated with lactic acidosis and is known to account for congenital lactic acidosis, recurrent ataxia, and infantile Leigh syndrome. Hitherto, however, peripheral neuropathy has not been regarded as a presenting symptom of pyruvate dehydrogenase deficiency. Here, we report on a boy who presented peripheral neuropathy with severe limb hypotonia, absent deep-tendon reflexes, and reduced motor nerve conduction velocities at 8 months of age. Persistent hyperpyruvicemia with normal lactate/pyruvate molar ratios in plasma were highly suggestive of a pyruvate dehydrogenase deficiency, and the determination of pyruvate dehydrogenase activity in circulating lymphocytes led to the diagnosis of pyruvate decarboxylase (PDH-E1) deficiency in the proband. Based on this observation, we suggest that pyruvate dehydrogenase deficiency should be considered in the diagnosis of peripheral neuropathy in infancy, especially when associated with persistent hyperpyruvicemia, normal lactate/pyruvate molar ratios in plasma, and recurrent episodes of drowsiness and hypotonia of unknown origin.

Brain↗
PubMed1998

Partial purification and characterization of the maize mitochondrial pyruvate dehydrogenase complex

The pyruvate dehydrogenase complex was partially purified and characterized from etiolated maize (Zea mays L.) shoot mitochondria. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed proteins of 40, 43, 52 to 53, and 62 to 63 kD. Immunoblot analyses identified these proteins as the E1beta-, E1alpha-, E2-, and E3-subunits, respectively. The molecular mass of maize E2 is considerably smaller than that of other plant E2 subunits (76 kD). The activity of the maize mitochondrial complex has a pH optimum of 7.5 and a divalent cation requirement best satisfied by Mg2+. Michaelis constants for the substrates were 47, 3, 77, and 1 &mgr;m for pyruvate, coenzyme A (CoA), NAD+, and thiamine pyrophosphate, respectively. The products NADH and acetyl-CoA were competitive inhibitors with respect to NAD+ and CoA, and the inhibition constants were 15 and 47 &mgr;m, respectively. The complex was inactivated by phosphorylation and was reactivated after the removal of ATP and the addition of Mg2+.

Journal Article↗