PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Pyruvate Synthase”

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 55 records · Page 3Linked to original sources
PubMed1970

Carbon dioxide fixation in green sulphur bacteria.

1. About one-third of the CO(2) fixed during photosynthesis by washed suspensions of Chlorobium thiosulfatophilum strain 8346 gave rise to alpha-oxoglutarate and branched-chain oxo acids, mainly beta-methyl-alpha-oxovalerate. Another one-third to one-half gave rise to a polyglucose. 2. The fixation of CO(2) was inhibited by fluoroacetate, increasing concentrations up to 1mm stimulating the accumulation of alpha-oxoglutarate and causing a decrease in the formation of the branched-chain oxo acids and polyglucose. 3. Acetate was converted into the same products as was CO(2). 4. Fluoroacetate (1mm) had a negligible effect on the formation of polyglucose from acetate and caused a slight inhibition of the formation of the branched-chain oxo acids and increased accumulation of alpha-oxoglutarate. 5. Iodoacetate (1mm) strongly inhibited polyglucose formation from acetate and caused accumulation of pyruvate. The formation of the branched-chain oxo acids from acetate was only slightly affected by this inhibitor. 6. Pyruvate can be metabolized by this organism in the presence of a suitable electron donor whether CO(2) is present or not. In the absence of CO(2) pyruvate is converted into polyglucose. 7. The accumulation of oxo acids during CO(2) fixation is completely inhibited by NH(4) (+) ions. The formation of the branched-chain oxo acids is considerably decreased by the presence of isoleucine, leucine or valine, or a mixture of these. 8. CO(2) fixation in two other strains of Chlorobium appears to exhibit a similar pattern to that in C. thiosulfatophilum strain 8346. 9. It is concluded that in washed suspensions, CO(2) is fixed mainly by a mechanism involving the reductive carboxylic acid cycle. Acetate, the product of the cycle, is converted into polyglucose via pyruvate synthase and a reversal of glycolysis or into branched-chain oxo acids by an unknown mechanism.

Acetates↗
PubMed1989

Unusual histochemical pattern in preneoplastic hepatic foci characterized by hyperactivity of several enzymes.

In a stop-experiment using the hepatocarcinogen N-nitrosomorpholine, as well as glycogenotic and related lesions, hepatocellular foci with a different histochemical pattern were identified. The outstanding features of these hepatic foci, which may progress to hepatocellular adenoma, were increased activities of mitochondrial glycerol-3-phosphate dehydrogenase (mG3PD), glycogen synthase, pyruvate kinase and glucose-6-phosphatase detected by enzyme histochemistry. Since no decrease in activity of any of the enzymes examined were seen in these foci, compared with normal liver, the term enzymatically hyperactive focus (EHF) is proposed for this type of lesion. Only at the stage of overtly nodular growth did these lesions exhibit some of the characteristic changes seen in nodules developing from glycogenotic foci, namely elevated activities of glucose-6-phosphate dehydrogenase, gamma-glutamyl transferase and glutathione-S-transferase P as well as decreased activities of adenosine-triphosphatase, glucose-6-phosphatase and adenylate cyclase. Some of these enzymes have been used widely in morphometric studies as markers for preneoplastic and neoplastic lesions. The inability to detect early EHF may lead to an underestimation of preneoplastic liver lesions in quantitative studies. Although there are apparent differences in the histochemical patterns of glycogen storing foci and early EHF, these differences tend to disappear during progression to overtly neoplastic lesions. In studies comparing the phenotypic alterations in different types of preneoplastic hepatic lesions, the recognition of EHF may contribute to the distinction of obligatory from facultative phenomena during transformation.

Adenoma↗
PubMed1979

Ferredoxin degradation in growing Clostridium pasteurianum during periods of iron deprivation.

Clostridium pasteurianum was grown in batch cultures on media with an initial iron concentration of 10 micron. The uptake of iron and the synthesis of ferredoxin was followed. All the iron present in the medium was taken up by the cells before 50% of the final cell density was attained. The bacteria then continued to grow in the complete absence of exogenous iron. Ferrodoxin was synthesized during growth until the exogenous iron concentration dropped below 1 micron. During growth in the absence of iron ferredoxin was degraded with the result that at the end of growth the cells did not contain ferredoxin. The specific activity of the iron sulfur protein, pyruvate synthase (E.C. 1.2.7.1), remained constant during growth of C. pasteurianum in the absence of exogenous iron. This finding suggest that ferredoxin was used as an endogenous source of iron for the synthesis of essential iron proteins during periods of iron deprivation.

Biodegradation, Environmental↗
PubMed1991

Oxygenase side reactions of acetolactate synthase and other carbanion-forming enzymes.

Enzymes that mediate carbanion chemistry must protect their reactants from solvent and undesirable electrophiles, such as molecular oxygen. A number of enzymes that utilize carbanionic intermediates were surveyed for O2-consuming side reactions. Several of these enzymes, acetolactate synthase, pyruvate decarboxylase, class II aldolase, and glutamate decarboxylase, catalyze previously undetected oxygen-consuming reactions, while others such as class I aldolase, [(phosphoribosyl)amino]imidazole carboxylase, 6-phosphogluconate dehydrogenase, isocitrate dehydrogenase, and triosephosphate isomerase do not. Prior to this work, only ribulosebisphosphate carboxylase was known to catalyze an oxygenase side reaction. These new example indicate that while O2-consuming side reactions are a more general feature of enzyme-mediated carbanion chemistry than has been previously appreciated, they are not necessarily an inevitable consequence of this chemistry. Expression of an oxygenase activity not only depends on the accessibility of the carbanionic intermediate to molecular oxygen but also may depend on the ability of the enzyme to stabilize the initially formed peroxide anion either through protonation with an appropriate enzymic group or through metal coordination.

Acetolactate Synthase↗
PubMed1978

Pyruvate-to-ethanol pathway in Entamoeba histolytica.

The pyruvate-to-ethanol pathway in Entamoeba histolytica is unusual when compared with most investigated organisms. Pyruvate decarboxylase (EC 4.1.1.1), a key enzyme for ethanol production, is not found. Pyruvate is converted into acetyl-CoA and CO2 by the enzyme pyruvate synthase (EC 1.2.7.1), which has been demonstrated previously in this parasitic amoeba. Acetyl-CoA is reduced to acetaldehyde and CoA by the enzyme aldehyde dehydrogenase (acylating) (EC 1.2.1.10) at an enzyme activity of 9 units per g of fresh cells with NADH as a reductant. Acetaldehyde is further reduced by either a previously identified NADP+-linked alcohol dehydrogenase or by a newly found NAD+-linked alcohol dehydrogenase at an enzyme activity of 136 units per g of fresh cells. Ethanol is identified as the product of soluble enzymes of amoeba acting on pyruvate or acetyl-CoA. This result is confirmed by radioactive isotopic, spectrophotometric and gas-chromatographic methods.

Acetaldehyde↗
PubMed1977

Oxidoreductases involved in cell carbon synthesis of Methanobacterium thermoautotrophicum.

Cell-free extracts of Methanobacterium thermoautotrophicum were found to contain high activities of the following oxidoreductases (at 60 degrees C): pyruvate dehydrogenase (coenzyme A acetylating), 275 nmol/min per mg of protein; alpha-ketoglutarate dehydrogenase (coenzyme A acylating), 100 nmol/min per mg; fumarate reductase, 360 nmol/min per mg; malate dehydrogenase, 240 nmol/min per mg; and glyceraldehyde-3-phosphate dehydrogenase, 100 nmol/min per mg. The kinetic properties (apparent V(max) and K(M) values), pH optimum, temperature dependence of the rate, and specificity for electron acceptors/donors of the different oxidoreductases were examined. Pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase were shown to be two separate enzymes specific for factor 420 rather than for nicotinamide adenine dinucleotide (NAD), NADP, or ferredoxin as the electron acceptor. Both activities catalyzed the reduction of methyl viologen with the respective alpha-ketoacid and a coenzyme A-dependent exchange between the carboxyl group of the alpha-ketoacid and CO(2). The data indicate that the two enzymes are similar to pyruvate synthase and alpha-ketoglutarate synthase, respectively. Fumarate reductase was found in the soluble cell fraction. This enzyme activity coupled with reduced benzyl viologen as the electron donor, but reduced factor 420, NADH, or NADPH was not effective. The cells did not contain menaquinone, thus excluding this compound as the physiological electron donor for fumarate reduction. NAD was the preferred coenzyme for malate dehydrogenase, whereas NADP was preferred for glyceraldehyde-3-phosphate dehydrogenase. The organism also possessed a factor 420-dependent hydrogenase and a factor 420-linked NADP reductase. The involvement of the described oxidoreductases in cell carbon synthesis is discussed.

Anaerobiosis↗
PubMed2003

Comparative genome- and proteome analysis of cerebral cortex from MK-801-treated rats.

cDNA microarrays and two-dimensional gel-electrophoresis in combination with mass spectrometry, were used to screen alterations in mRNA and protein levels, respectively, in cerebral cortex of MK-801-treated rats. The rats were divided in two groups; group 1 (short-term treated) and group 2 (long-term treated). In group 1, four genes were up-regulated and five down-regulated. In group 2, seven genes were up-regulated and six down-regulated. In group 1, the levels of one protein was increased and eight proteins reduced. In group 2, the levels of two proteins were increased and four proteins reduced. Several of the altered genes (casein kinase 2, glutamic acid decarboxylase, synaptotagmin, gamma aminobutyric acid [GABA] transporter, creatine kinase, and cytochrome c oxidase) and proteins (superoxide dismutase, hsp 60, hsp 72 and gamma-enolase) have previously been connected to schizophrenia. Alterations of the genes (microglobulin, c-jun proto-oncogene, 40S ribosomal protein S19, adenosine diphosphate (ADP)-ribosylation factors, platelet-derived growth factor, fructose-bisphophate aldolase A, and myelin proteolipid) and the proteins (stathmin, H+-transp. Adenosine triphosphate (ATP) synthase, pyruvate dehydrogenase, beta-actin and alpha-enolase), have not, to our knowledge, earlier been implicated in schizophrenia pathology. Overall, these results with a combined approach of genomics and proteomics add to the validity of subchronic N-methyl-D-aspartate (NMDA)-receptor antagonist treatment as an animal model of schizophrenia.

Animals↗
PubMed2004

Unique sugar metabolism and novel enzymes of hyperthermophilic archaea.

Hyperthermophiles are a group of microorganisms that have their optimum growth temperature above 80 degrees C. More than 60 species of the hyperthermophiles have been isolated from marine and continental volcanic environments. Most hyperthermophiles belong to Archaea, the third domain of life, and are considered to be the most ancient of all extant life forms. Recent studies have revealed the presence of unusual sugar metabolic processes in hyperthermophilic archaea, for example, a modified Embden-Meyerhof pathway, that has so far not been observed in bacteria and eucarya. Several novel enzymes, such as ADP-dependent glucokinase, ADP-dependent phosphofructokinase, glyceraldehyde-3-phosphate ferredoxin oxidoreductase, phosphoenolpyruvate synthase, pyruvate : ferredoxin oxidoreductase, and ADP-forming acetyl-CoA synthetase, have been found to be involved in a modified Embden-Meyerhof pathway of the hyperthermophilic archaeon Pyrococcus furiosus. In addition, a unique mode of ATP regeneration has been postulated to exist in the pathway of P. furiosus. The metabolic design observed in this microorganism might reflect the situation at an early stage of evolution.

Amino Acid Sequence↗
PubMed1997

The three-dimensional structure of flavodoxin reductase from Escherichia coli at 1.7 A resolution.

Flavodoxin reductase from Escherichia coli is an FAD-containing oxidoreductase that transports electrons between flavodoxin or ferredoxin and NADPH. Together with flavodoxin, the enzyme is involved in the reductive activation of three E. coli enzymes: cobalamin-dependent methionine synthase, pyruvate formate lyase and anaerobic ribonucleotide reductase. An additional function for the oxidoreductase appears to be to protect the bacteria against oxygen radicals. The three-dimensional structure of flavodoxin reductase has been solved by multiple isomorphous replacement, and has been refined at 1.7 A to an R-value of 18.4% and Rfree 24.8%. The monomeric molecule contains one beta-sandwich FAD domain and an alpha/beta NADP domain. The overall structure is similar to other reductases of the NADP-ferredoxin reductase family in spite of the low sequence similarities within the family. Flavodoxin reductase lacks the loop which is involved in the binding of the adenosine moiety of FAD in other FAD binding enzymes of the superfamily but is missing in the FMN binding phthalate dioxygenase reductase. Instead of this loop, the adenine interacts with an extra tryptophan at the C terminus. The FAD in flavodoxin reductase has an unusual bent conformation with a hydrogen bond between the adenine and the isoalloxazine. This is probably the cause of the unusual spectrum of the enzyme. There is a pronounced cleft close to the isoalloxazine that appears to be well suited for binding of flavodoxin/ferredoxin. Two extra short strands of the NADP-binding domain probably act as an anchor point for the binding of flavodoxin.

Adenosine↗
PubMed1992

Clostridium neopropionicum sp. nov., a strict anaerobic bacterium fermenting ethanol to propionate through acrylate pathway.

Strain X4 was isolated several years ago from an anaerobic mesophilic plant treating vegetable cannery waste waters. It was the first example of propionic fermentation from ethanol. Morphologic and physiologic characterizations of the strain are presented here. This strain is described as type strain of a new species, Clostridium neopropionicum sp. nov. Whole cells of strain X4 ferment [1-13C] ethanol and CO2 to [2-13C] propionate, [1-13C] acetate and [2-13C] propanol, suggesting the absence of a randomizing pathway during the propionate formation. Enzymes involved in this fermentation were assayed in cell-free extracts of cells grown with ethanol as sole substrate. Alcohol dehydrogenase, aldehyde dehydrogenase, phosphate acetyl transferase, acetate kinase, pyruvate synthase, lactate dehydrogenases, and the enzymes of the acrylate pathway were detected at activities sufficient to be involved in ethanol fermentation. The same pathway may be used for the degradation of lactate or acrylate to acetate.

Acrylates↗
PubMed1995

Pyruvate: ferredoxin oxidoreductase from the sulfate-reducing Archaeoglobus fulgidus: molecular composition, catalytic properties, and sequence alignments.

Archaeoglobus fulgidus is a hyperthermophilic sulfate-reducing archaeon. In this communication we describe the purification and properties of pyruvate: ferredoxin oxidoreductase from this organism. The catabolic enzyme was purified 250-fold to apparent homogeneity with a yield of 16%. The native enzyme had an apparent molecular mass of 120 kDa and was composed of four different subunits of apparent molecular masses of 45, 33, 25, and 13 kDa, indicating an alpha beta gamma delta structure. Per mol, the enzyme contained 0.8 mol thiamine pyrophosphate, 9 mol non-heme iron, and 8 mol acid-labile sulfur. FAD, FMN, lipoic acid, and copper were not found. The purified enzyme showed an apparent Km for coenzyme A of 0.02 mM, for pyruvate of 0.3 mM, and for clostridial ferredoxin of 0.01 mM, an apparent Vmax of 64 U/mg (at 65 degrees C) with a pH optimum near 7.5 and an Arrhenius activation energy of 75 kJ/mol (between 30 and 70 degrees C). The temperature optimum was above 90 degrees C. At 90 degrees C, the enzyme lost 50% activity within 60 min in the presence of 2 M KCl. The enzyme did not catalyze the oxidation of 2-oxoglutarate, indolepyruvate, phenylpyruvate, glyoxylate, and hydroxypyruvate. The N-terminal amino acid sequences of the four subunits were determined. The sequence of the alpha-subunit had similarities to the N-terminal amino acid sequence of the alpha-subunit of the heterotetrameric pyruvate: ferredoxin oxidoreductase from Pyrococcus furiosus and from Thermotoga maritima, and unexpectedly, to the N-terminal amino acid sequence of the homodimeric pyruvate:ferredoxin oxidoreductase from proteobacteria and from cyanobacteria. No sequence similarities were found, however, between the alpha-subunits of the enzyme from A. fulgidus and the heterodimeric pyruvate:ferredoxin oxidoreductase from Halobacterium halobium.

Amino Acid Sequence↗
PubMed1995

Electron transport phosphorylation driven by glyoxylate respiration with hydrogen as electron donor in membrane vesicles of a glyoxylate-fermenting bacterium.

The syntrophically glycolate-fermenting bacterium in the methanogenic binary coculture FlGlyM was isolated in pure culture (strain FlGlyR) with glyoxylate as sole substrate. This strain disproportionated 12 glyoxylate to 7 glycolate, 10 CO2, and 3 hydrogen. Glyoxylate was oxidized via the malyl-CoA pathway. All enzymes of this pathway, i.e. malyl-CoA lyase/malate: CoA ligase, malic enzyme, and pyruvate synthase, were demonstrated in cell-free extracts. Glycolate dehydrogenase, hydrogenase, and ATPase, as well as menaquinones as potential electron carriers, were present in the membranes. Everted membrane vesicles catalyzed hydrogen-dependent glyoxylate reduction to glycolate [86-207 nmol min-1 (mg protein)-1] coupled to ATP synthesis from ADP and Pi [38-82 nmol min-1 (mg protein)-1)]. ATP synthesis was abolished entirely by protonophores or ATPase inhibitors (up to 98 and 94% inhibition, respectively) indicating the involvement of proton-motive force in an electron transport phosphorylation driven by a new glyoxylate respiration with hydrogen as electron donor. Measured reaction rates in vesicle preparations revealed a stoichiometry of ATP formation of 0.2-0.5 ATP per glyoxylate reduced.

Adenosine Triphosphate↗
PubMed2003

The importance of porE and porF in the anabolic pyruvate oxidoreductase of Methanococcus maripaludis.

The operon of the anabolic pyruvate oxidoreductase (POR) of Methanococcus maripaludis encodes two genes ( porEF) whose functions are unknown. Because these genes possess sequence similarity to polyferredoxins, they may be electron carriers to the POR. To elucidate whether the methanococcal POR requires PorEF for activity, a deletion mutant, strain JJ150, lacking porEF was constructed. Compared to the wild-type strain JJ1, the mutant grew more slowly in minimal medium and minimal plus acetate medium, and pyruvate-dependent methanogenesis was inhibited. In contrast, the methyl-viologen-dependent pyruvate-oxidation activity of POR, carbon monoxide dehydrogenase, and hydrogenase activities of the mutant were similar to those of the wild-type. Upon genetic complementation of the mutant with porEF in the methanococcal shuttle vector pMEV2+ porEF, growth in minimal medium and pyruvate-dependent methanogenesis were restored to wild-type levels. Complementation with porE alone restored methanogenesis from pyruvate but not growth in minimal medium. Complementation with porF alone partially restored growth but not methanogenesis from pyruvate. Although the specific roles of porE and porF have not been determined, these results suggest that PorEF play important roles in the anabolic POR in vivo even though they are not required for the dye-dependent activity.

Aldehyde Oxidoreductases↗
PubMed2001

Direct electrochemical characterization of hyperthermophilic Thermococcus celer metalloenzymes involved in hydrogen production from pyruvate.

The reduction potentials of the metalloproteins pyruvate ferredoxin oxidoreductase (POR), ferredoxin, and hydrogenase isolated from hyperthermophilic Thermococcus celer (Topt = 88 degrees C) were determined as a function of temperature from 10 to 85 degrees C. Square-wave voltammetry experiments were carried out on 15 microL samples directly at an unmodified "edge-polished" pyrolytic graphite electrode using MgCl2 as an electrode promoter. POR exhibited two voltammetric waves with peaks at -280 and -403 mV at room temperature, indicating multiple redox centers, and a single wave at -420 mV at 85 degrees C. These waves displayed different temperature-dependent peak positions and peak heights, indicating that these redox centers have different thermodynamic and kinetic properties. Ferredoxin displayed a single linear temperature-dependent voltammetric wave at -280 mV at room temperature and -327 mV at 85 degrees C. Hydrogenase displayed a single biphasic temperature-dependent voltammetric wave at -197 mV at room temperature and -211 mV at 85 degrees C. Thermodynamic parameters associated with electron transfer, namely standard enthalpies and entropies for the redox centers in the various proteins, are reported.

Electrochemistry↗
PubMed1996

Molecular mechanism of pyruvate-ferredoxin oxidoreductases based on data obtained with the Clostridium pasteurianum enzyme.

Pyruvate-ferredoxin oxidoreductase oxidises pyruvate in many fermentative microorganisms. The enzyme from Clostridium pasteurianum is an air-sensitive homodimer of 2x120000 daltons, for which pyruvate is the best substrate found among several alpha-ketoacids. Each subunit contains eight iron atoms in two [4Fe-4S] clusters. Two distinct EPR signals, possibly associated with two ligand environments, arise from one of these clusters. Binding of pyruvate does not generate a radical. The results reported suggest a scheme for the electron flow in pyruvate ferredoxin oxidoreductases according to which the detailed reaction mechanism depends on the number (even or odd) of [4Fe-4S] clusters present in a given enzyme.

Catalysis↗
PubMed1984

Metabolic differences between metronidazole resistant and susceptible strains of Tritrichomonas foetus.

Tritrichomonas foetus mutants resistant to metronidazole lack the hydrogenosomal enzymes pyruvate: ferredoxin oxidoreductase and hydrogenase. Hydrogenosomes of these organisms did not oxidize pyruvate or produce ATP in its presence. Elimination of hydrogenosomal metabolism of pyruvate was compensated by an increased rate of glycolysis. The resistant mutants excreted no organic acids and H2 as metabolic end products. Glycolysis of the resistant T. foetus KV1-1MR-100 can be summarized as 1 mol glucose----2 mol ethanol + 2 mol CO2. The parent strain KV1, excreting H2, CO2 and acidic end products, converted about 10% of glucose to ethanol. Both strains produced ethanol from pyruvate through the action of two cytoplasmic enzymes: pyruvate decarboxylase and alcohol dehydrogenase. The specific activity of the former enzyme, catalyzing nonoxidative decarboxylation of pyruvate to acetaldehyde, was nearly seven times higher in the resistant than in the parent strain. Alcohol dehydrogenase reducing acetaldehyde to ethanol was specific to NADPH; it catalyzed the reverse reaction only slowly, and displayed similar activities in both resistant and sensitive trichomonads. Development of anaerobic metronidazole resistance in T. foetus depended on the loss of pyruvate:ferredoxin oxidoreductase as well as on the ability to increase alcoholic fermentation.

Alcohol Dehydrogenase↗
PubMed1986

Anaerobic pyruvate metabolism of Tritrichomonas foetus and Trichomonas vaginalis hydrogenosomes.

Hydrogenosomes isolated from Tritrichomonas foetus and Trichomonas vaginalis fermented pyruvate to acetate, malate, H2, and CO2 in an anaerobic process dependent on ADP, Pi, Mg2+, and succinate. The extent to which pyruvate was carboxylated to malate by malate dehydrogenase (decarboxylating) rather than decarboxylated to acetate by pyruvate/ferredoxin oxidoreductase was dependent on pCO2. The processes observed showed carbon and redox balances. The presence of an NADH/ferredoxin oxidoreductase activity was demonstrated. This enzyme is likely to be involved in the transfer of electrons from the ferredoxin reduced in pyruvate oxidation to NAD+ needed for the reductive carboxylation of pyruvate. Disruption of hydrogenosomes with Triton X-100 led to cessation of pyruvate-dependent H2 formation which could be restored by addition of coenzyme A and methyl viologen or ferredoxin. The formation of acetate and H2 by undisrupted hydrogenosomes proceeded at approximately half maximal rates in the presence of 25 microM succinate for T. foetus and 5 microM succinate for T. vaginalis. The apparent Km value of the acetate/succinate CoA transferase from T. foetus for succinate was approximately 45 microM, thus the stimulating effect of succinate might be due to the requirement of this enzyme for succinate. The exact mechanism of this effect remains to be elucidated, however.

Acetates↗