SEARCH · Search PubMed

Results for “Pyruvates”

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.

SourceResearch connectionFrom yearThrough year

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

At least 1,081 records · Page 60Linked to original sources

PubMed1985

The sub-cellular localisation and regulatory properties of pyruvate carboxylase from Rhizopus arrhizus.

Cell-free extracts of Rhizopus arrhizus contain exclusively cytosolic pyruvate carboxylase and NAD-glutamate dehydrogenase, a single mitochondrial isoenzyme of NADP-isocitrate dehydrogenase, and both mitochondrial and cytosolic isoenzymes of NADP-malate dehydrogenase (decarboxylating). Other enzymes examined have sub-cellular localisations similar to those characteristic of mammalian liver. Purified preparations of R. arrhizus pyruvate carboxylase are subject to partial regulatory inhibition by L-aspartate and 2-oxoadipate. L-Glutamate acts as a less effective analogue of L-aspartate while 2-oxoglutarate is ineffective. Competition studies indicate the presence of separate inhibitory sites for L-aspartate and 2-oxoadipate. Under routine assay conditions R. arrhizus pyruvate carboxylase shows significant activation by acyl derivatives of coenzyme A with long chain acyl CoA being more effective than acetyl-CoA. This activation is no longer observed in the presence of high concentrations of pyruvate, MgATP2- and HCO-3. The concentrations of L-aspartate and 2-oxoadipate required to give 50% inhibition ([I]0.5), and the maximal extents of inhibition, are increased by addition of acetyl-CoA. Acetyl-CoA increases the sigmoidal character of the relationship: initial rate/[L-aspartate], but decreases this parameter for the relationship: initial rate/[2-oxoadipate]. The studies indicate that R. arrhizus possesses an entirely cytosolic pathway for the conversion of glucose to fumaric acid and that both the organisation of pyruvate metabolism and the regulation of pyruvate carboxylase differ significantly in this organism as compared to that proposed previously for Aspergillus nidulans.

Acetyl Coenzyme A↗

PubMed1981

The effect of cyanamide on acetaldehyde oxidation by isolated rat liver mitochondria and on the inhibition of pyruvate oxidation by acetaldehyde.

Compared to other substrates, the oxidation of pyruvate by isolated mitochondria is especially sensitive to inhibition by acetaldehyde. It is not known whether this inhibition represents a direct effect of acetaldehyde or requires the metabolism of acetaldehyde. Experiments were therefore carried out in the presence of cyanamide, an inhibitor of aldehyde dehydrogenase. After a brief incubation period, cyanamide inhibited the state 4 and state 3 rate of acetaldehyde (0.1-1.0 mM) oxidation by isolated rat liver mitochondria. Little inhibition was found in the absence of the incubation period. Maximum inhibition was found at cyanamide concentrations of 0.01 to 0.033 mM. Cyanamide also inhibited the activity of aldehyde dehydrogenase assayed in disrupted mitochondrial fractions. The inhibition by cyanamide was specific since cyanamide did not affect mitochondrial oxidation of succinate, glutamate, or pyruvate. Acetaldehyde inhibited the state 3 rate of pyruvate oxidation by liver mitochondria. Despite preventing acetaldehyde oxidation, cyanamide did not prevent the inhibition of pyruvate oxidation by acetaldehyde. These results indicate that (a) cyanamide can be used as an effective in vitro inhibitor of acetaldehyde oxidation and (b) the unique sensitivity of pyruvate oxidation to acetaldehyde represents a direct effect of acetaldehyde on pyruvate dehydrogenase.

Acetaldehyde↗

PubMed1982

Interaction between drug acetylation and ethanol, acetate, pyruvate, citrate, and L(-) carnitine in isolated rat liver parenchymal cells.

The acetylation of sulfanilamide and procainamide in suspensions of isolated rat parenchymal cells was studied in absence and presence of ethanol (33mM), citrate (4 mM), pyruvate (4 mM), and L(-)carnitine (2 mM). Ethanol treatment enhanced the sulfanilamide acetylation whereas the acetylation of procainamide was considered to be unchanged. Acetate (1-5 mM), citrate, and pyruvate treatment enhanced the acetylation of both sulfanilamide and procainamide. Acetate (4 mM) increased both Km and Vmax of both sulfanilamide and procainamide acetylation. Combined treatment with L(-)carnitine and either acetate, pyruvate, or citrate enhanced the acetylation rate of sulfanilamide more than acetate, pyruvate, or citrate, respectively alone. In cell suspensions treated with L(-) carnitine and acetate or pyruvate, the acetylation kinetics of sulfanilamide changed from zero-to apparent first-order. With procainamide as test drug, a further increase of the acetylation rate was found when L(-) carnitine was added to citrate pyruvate. Acetyl-CoA increased the rate of sulfanilamide acetylation in rat liver homogenates in a dose dependent manner.

Acetates↗

PubMed2006

Involvement of pyruvate oxidase activity and acetate production in the survival of Lactobacillus plantarum during the stationary phase of aerobic growth.

In addition to the previously characterized pyruvate oxidase PoxB, the Lactobacillus plantarum genome encodes four predicted pyruvate oxidases (PoxC, PoxD, PoxE, and PoxF). Each pyruvate oxidase gene was individually inactivated, and only the knockout of poxF resulted in a decrease in pyruvate oxidase activity under the tested conditions. We show here that L. plantarum has two major pyruvate oxidases: PoxB and PoxF. Both are involved in lactate-to-acetate conversion in the early stationary phase of aerobic growth and are regulated by carbon catabolite repression. A strain devoid of pyruvate oxidase activity was constructed by knocking out the poxB and poxF genes. In this mutant, acetate production was strongly affected, with lactate remaining the major end product of either glucose or maltose fermentation. Notably, survival during the stationary phase appeared to be dramatically improved in the poxB poxF double mutant.

Acetates↗

PubMed2002

Effect of pyruvate carboxylase overexpression on the physiology of Corynebacterium glutamicum.

Pyruvate carboxylase was recently sequenced in Corynebacterium glutamicum and shown to play an important role of anaplerosis in the central carbon metabolism and amino acid synthesis of these bacteria. In this study we investigate the effect of the overexpression of the gene for pyruvate carboxylase (pyc) on the physiology of C. glutamicum ATCC 21253 and ATCC 21799 grown on defined media with two different carbon sources, glucose and lactate. In general, the physiological effects of pyc overexpression in Corynebacteria depend on the genetic background of the particular strain studied and are determined to a large extent by the interplay between pyruvate carboxylase and aspartate kinase activities. If the pyruvate carboxylase activity is not properly matched by the aspartate kinase activity, pyc overexpression results in growth enhancement instead of greater lysine production, despite its central role in anaplerosis and aspartic acid biosynthesis. Aspartate kinase regulation by lysine and threonine, pyruvate carboxylase inhibition by aspartate (shown in this study using permeabilized cells), as well as well-established activation of pyruvate carboxylase by lactate and acetyl coenzyme A are the key factors in determining the effect of pyc overexpression on Corynebacteria physiology.

Aspartic Acid↗

PubMed2002

Effects of growth mode and pyruvate carboxylase on succinic acid production by metabolically engineered strains of Escherichia coli.

Escherichia coli NZN111, which lacks activities for pyruvate-formate lyase and lactate dehydrogenase, and AFP111, a derivative which contains an additional mutation in ptsG (a gene encoding an enzyme of the glucose phophotransferase system), accumulate significant levels of succinic acid (succinate) under anaerobic conditions. Plasmid pTrc99A-pyc, which expresses the Rhizobium etli pyruvate carboxylase enzyme, was introduced into both strains. We compared growth, substrate consumption, product formation, and activities of seven key enzymes (acetate kinase, fumarate reductase, glucokinase, isocitrate dehydrogenase, isocitrate lyase, phosphoenolpyruvate carboxylase, and pyruvate carboxylase) from glucose for NZN111, NZN111/pTrc99A-pyc, AFP111, and AFP111/pTrc99A-pyc under both exclusively anaerobic and dual-phase conditions (an aerobic growth phase followed by an anaerobic production phase). The highest succinate mass yield was attained with AFP111/pTrc99A-pyc under dual-phase conditions with low pyruvate carboxylase activity. Dual-phase conditions led to significant isocitrate lyase activity in both NZN111 and AFP111, while under exclusively anaerobic conditions, an absence of isocitrate lyase activity resulted in significant pyruvate accumulation. Enzyme assays indicated that under dual-phase conditions, carbon flows not only through the reductive arm of the tricarboxylic acid cycle for succinate generation but also through the glyoxylate shunt and thus provides the cells with metabolic flexibility in the formation of succinate. Significant glucokinase activity in AFP111 compared to NZN111 similarly permits increased metabolic flexibility of AFP111. The differences between the strains and the benefit of pyruvate carboxylase under both exclusively anaerobic and dual-phase conditions are discussed in light of the cellular constraint for a redox balance.

Aerobiosis↗

PubMed1996

Regulation of gonococcal sialyltransferase, lipooligosaccharide, and serum resistance by glucose, pyruvate, and lactate.

Strain F62 of Neisseria gonorrhoeae gonococci (GC) is sensitive to normal human serum unless CMP-N-acetylneuraminic acid (CMP-NANA) is present. NANA is transferred primarily to a 4.5-kDa lipooligosaccharide (LOS) structure by a GC sialyltransferase (Stase). We investigated LOS and Stase expression and serum resistance in strain F62 grown in different carbon sources and growth conditions. Pyruvate-grown GC expressed 1.9- to 5.6-fold more Stase activity than did glucose-grown GC, whereas lactate-grown GC generally expressed intermediate Stase activities. Broth-grown GC expressed two- to fourfold more Stase activity than did plate-grown GC in all carbon sources. Pyruvate- or lactate-grown GC expressed significantly more of the sialylateable 4.5-kDa LOS species than did glucose-grown GC. Anaerobically, the 4.5-kDa LOS species was expressed in greater quantity than the 4.9-kDa N-acetyl galactosamine-terminating species in all carbon sources. Pyruvate-grown GC also incorporated up to threefold more radiolabelled CMP-NANA onto the 4.5-kDa LOS species than did glucose-grown GC. In serum resistance studies, pyruvate-grown GC were 6.5- to 16.1-fold more serum resistant than glucose-grown GC at limiting CMP-NANA concentrations (1.56 to 12.50 microg/ml). Taken together, these results indicate that gonococcal expression of Stase activity is up-regulated by growth in pyruvate or lactate, which correlates with enhanced expression of the sialylateable 4.5-kDa LOS and, for growth in pyruvate, correlates with enhanced sialylation of gonococcal LOS and greater serum resistance. In different in vivo niches, gonococcal LOS sialylation, serum resistance, and interaction with host cells can be highly regulated.

Aerobiosis↗

PubMed1970

Basis of pyruvate inhibition in Thiobacillus thiooxidans.

Addition of 10(-3)m pyruvic acid to cultures of Thiobacillus thiooxidans, at pH 2.3, results in its rapid intracellular accumulation and in the cessation of sulfur oxidation, CO(2) fixation, and oxygen consumption; at pH 7.0, pyruvate neither inhibits oxygen uptake nor accumulates appreciably intracellularly. Pyruvate does not affect CO(2) fixation in cell-free extracts. The data suggest that the cells of T. thiooxidans are passively permeable to pyruvic acid at low pH. Thus entry of pyruvic acid causes accumulation of pyruvate with a concomitant decrease in intracellular pH.

Carbon Dioxide↗

PubMed1991

Characterization of PDC6, a third structural gene for pyruvate decarboxylase in Saccharomyces cerevisiae.

Pyruvate decarboxylase is the key enzyme in alcoholic fermentation in yeast. Two structural genes, PDC1 and PDC5 have been characterized. Deletion of either of these genes has little or no effect on the specific pyruvate decarboxylase activity, but enzyme activity is undetectable in mutants lacking both PDC1 and PDC5 (S. Hohmann and H. Cederberg, Eur. J. Biochem. 188:615-621, 1990). Here I describe PDC6, a gene structurally closely related to PDC1 and PDC5. The product of PDC6 does not seem to be required for wild-type pyruvate decarboxylase activity in glucose medium; delta pdc6 mutants have no reduced specific enzyme activity, and the PDC6 deletion did not change the phenotype or the specific enzyme activity of mutants lacking either or both of the other two structural genes. However, in cells grown in ethanol medium the PDC6 deletion caused a reduction of pyruvate decarboxylase activity. Northern (RNA) blot analysis showed that PDC6 is weakly expressed, and expression seemed to be higher during growth in ethanol medium. This behavior remained obscure since pyruvate decarboxylase catalyzes an irreversible reaction. Characterization of all combinations of PDC structural gene deletion mutants, which produce different amounts of pyruvate decarboxylase activity, showed that the enzyme is also needed for normal growth in galactose and ethanol medium and in particular for proper growth initiation of spores germinating on ethanol medium.

Amino Acid Sequence↗

PubMed1992

Identification and analysis of the genes coding for the putative pyruvate dehydrogenase enzyme complex in Acholeplasma laidlawii.

A monospecific antibody recognizing two membrane proteins in Acholeplasma laidlawii identified a plasmid clone from a genomic library. The nucleotide sequence of the 4.6-kbp insert contained four sequential genes coding for proteins of 39 kDa (E1 alpha, N terminus not cloned), 36 kDa (E1 beta), 57 kDa (E2), and 36 kDa (E3; C terminus not cloned). The N termini of the cloned E2, E1 beta, and native A. laidlawii E2 proteins were verified by amino acid sequencing. Computer-aided searches showed that the translated DNA sequences were homologous to the four subenzymes of the pyruvate dehydrogenase complexes from gram-positive bacteria and humans. The plasmid-encoded 57-kDa (E2) protein was recognized by antibodies against the E2 subenzymes of the pyruvate and oxoglutarate dehydrogenase complexes from Bacillus subtilis. A substantial fraction of the E2 protein as well as part of the pyruvate dehydrogenase enzymatic activity was associated with the cytoplasmic membrane in A. laidlawii. In vivo complementation with three different Escherichia coli pyruvate dehydrogenase-defective mutants showed that the four plasmid-encoded proteins were able to restore pyruvate dehydrogenase enzyme activity in E. coli. Since A. laidlawii lacks oxoglutarate dehydrogenase and most likely branched-chain dehydrogenase enzyme complex activities, these results strongly suggest that the sequenced genes code for the pyruvate dehydrogenase complex.

Acholeplasma laidlawii↗

PubMed1967

Transaminase activity and other enzymatic reactions involving pyruvate and glutamate in Chlamydia (psittacosis-trachoma group).

The agents of meningopneumonitis (MN) and of trachoma (TR) purified from chick embryo allantoic fluids and yolk sacs, respectively, were shown to produce CO(2) from the C(1) positions of pyruvate and glutamate, but not from the other carbon atoms. The reaction with pyruvate did not require did not require the addition of cofactors, but was stimulated to a small extent by alpha-lipoic acid and, in the case of TR, also by diphosphothiamine, and nicotinamide adenine dinucleotide (NAD). The reaction of MN with glutamate was greatly stimulated by the addition of NAD and pyruvate, and resulted in the accumulation of alanine. The reaction of TR with glutamate was also greatly enhanced by added NAD, but was not affected by added pyruvate. When eight intermediates of the citric acid cycle were added to MN cells incubated with glutamate-C(14), plus NAD and pyruvate, they reduced to varying degrees the evolution of C(14)O(2). It was shown by chromatography that the C(14) label extended to alpha-ketoglutarate and succinate, but not to fumarate and malate. A net gain in adenosine triphosphate could not be demonstrated in MN cells incubated with combined glutamate, pyruvate, oxaloacetate, and various cofactors. These results furnish additional examples of real or apparent gaps in enzyme sequences in Chlamydia.

Carbon Dioxide↗

PubMed1967

Pyruvate metabolism in Sarcina maxima.

The mechanisms of pyruvate cleavage and hydrogen production by Sarcina maxima were studied. It was found that a phosphoroclastic system for pyruvate oxidation, similar to that occurring in saccharolytic clostridia, is present in S. maxima. Cleavage of pyruvate by extracts of the latter organism resulted in the formation of acetyl phosphate, CO(2), and electrons which were transferred to ferredoxin. Formate was not an intermediate in this system. Pyruvate oxidation was coupled with ferredoxin-dependent nicotinamide adenine dinucleotide phosphate (NADP) reduction. A hydrogenase, active in particulate extracts of S. maxima, did not accept electrons from reduced ferredoxin. Formate was detected as a fermentation product when S. maxima was grown in media buffered with CaCO(3). Whole cells and extracts degraded formate to H(2) and CO(2). The evidence suggests that electrons generated by ferredoxin-linked pyruvate oxidation by S. maxima are not used for H(2) production, but that they serve for the reduction of NADP. Reduced NADP may be utilized by the organisms for synthesis of cell material. Production of H(2) by S. maxima may occur through a pyruvate clastic system similar to that present in coliform bacteria.

Acetates↗

PubMed1987

Some aspects of the regulation of pyruvate kinase levels in Neurospora crassa.

Pyruvate kinase levels were monitored in Neurospora crassa mycelium (grown on different carbon sources for varying time intervals) by immunoprecipitation using polyclonal antibodies raised against a purified enzyme preparation. Pyruvate kinase specific mRNA was demonstrated by hybridization of Northern and dot blots of total RNA with a N. crassa pyruvate kinase gene fragment. Two pyruvate kinase specific mRNA species were detected in mycelia of all ages examined. An age-dependent and carbon source dependent variation in the pyruvate kinase protein and mRNA levels was encountered: both registered an increase for up to about 20 h and a subsequent decline; growth on acetate and sucrose resulted in significantly higher yields of both, relative to that on medium containing ethanol and alanine. Stress caused by heat shock depressed the pyruvate kinase mRNA levels.

DNA Restriction Enzymes↗

PubMed2006

Pyruvate induces mitochondrial biogenesis by a PGC-1 alpha-independent mechanism.

Oxidative cells increase mitochondrial mass in response to stimuli such as changes in energy demand or cellular differentiation. This plasticity enables the cell to adapt dynamically to achieve the necessary oxidative capacity. However, the pathways involved in triggering mitochondrial biogenesis are poorly defined. The present study examines the impact of altering energy provision on mitochondrial biogenesis in muscle cells. C2C12 myoblasts were chronically treated with supraphysiological levels of sodium pyruvate for 72 h. Treated cells exhibited increased mitochondrial protein expression, basal respiratory rate, and maximal oxidative capacity. The increase in mitochondrial biogenesis was independent of increases in peroxisomal proliferator activator receptor-gamma coactivator-1alpha (PGC-1alpha) and PGC-1beta mRNA expression. To further assess whether PGC-1alpha expression was necessary for pyruvate action, cells were infected with adenovirus containing shRNA for PGC-1alpha before treatment with pyruvate. Despite a 70% reduction in PGC-1alpha mRNA, the effect of pyruvate was preserved. Furthermore, pyruvate induced mitochondrial biogenesis in primary myoblasts from PGC-1alpha null mice. These data suggest that regulation of mitochondrial biogenesis by pyruvate in myoblasts is independent of PGC-1alpha, suggesting the existence of a novel energy-sensing pathway regulating oxidative capacity.

Adaptation, Physiological↗

PubMed1998

Mitochondrial uncoupling protein may participate in futile cycling of pyruvate and other monocarboxylates.

The physiological role of monocarboxylate transport in brown adipose tissue mitochondria has been reevaluated. We studied pyruvate, alpha-ketoisovalerate, alpha-ketoisocaproate, and phenylpyruvate uniport via the uncoupling protein (UCP1) as a GDP-sensitive swelling in K+ salts induced by valinomycin or by monensin and carbonyl cyanide-p-(trifluoromethoxy)phenylhydrazone in Na+ salts. We have demonstrated that this uniport is inhibited by fatty acids. GDP inhibition in K+ salts was not abolished by an uncoupler, indicating a negligible monocarboxylic acid penetration via the lipid bilayer. In contrast, the electroneutral pyruvate uptake (swelling in ammonium pyruvate or potassium pyruvate induced by change in pH) mediated by the pyruvate carrier was inhibited by its specific inhibitor alpha-cyano-4-hydroxycinnamate but not by fatty acids. Moreover, alpha-cyano-4-hydroxycinnamate enhanced the energization of brown adipose tissue mitochondria, which was monitored fluorometrically by 2-(4-dimethylaminostyryl)-1-methylpyridinium iodide and safranin O. Consequently, we suggest that UCP1 might participate in futile cycling of unipolar ketocarboxylates under certain physiological conditions while expelling these anions from the matrix. The cycle is completed on their return via the pyruvate carrier in an H+ symport mode.

Adipose Tissue, Brown↗

PubMed1981

Regulation of pyruvate kinase by 6-phosphogluconate in isolated hepatocytes.

Isolated liver parenchymal cells from rats fed a 65% sucrose diet for 14 days were incubated in the presence and absence of 10(-6) M glucagon. The pyruvate kinase obtained from homogenates of the glucagon-treated cells displayed and increased Ks 0.5 for phosphoenolpyruvate (P-enolpyruvate), as well as an increased Ka 0.5 for 6-phosphogluconate (6-P-gluconate), compared to pyruvate kinase from untreated cells. Additionally, glucagon treatment decreased the maximal stimulation of pyruvate kinase by 6-P-gluconate by approximately two-thirds and decreased the Hill coefficient value of pyruvate kinase for 6-P-gluconate from 1.76 to 1.56. 6-Aminonicotinamide, an inhibitor of 6-P-gluconate dehydrogenase, increased 6-P-gluconate levels in isolated liver parenchymal cells three- to sevenfold, depending on the substrates present. The flux of P-enolpyruvate through pyruvate kinase was increased from 18 to 40% in these preparations and was highly correlated with the increase in 6-P-gluconate levels. The results suggest that 6-P-gluconate could regulate pyruvate kinase activity in the intact liver parenchymal cell. Furthermore, the activator would be of greatest importance in the lipogenic animal.

Animals↗

PubMed1988

Evaluation of the isotopic equilibration between lactate and pyruvate.

When an isotopic tracer is infused for the purpose of determining the rate of turnover or oxidation of a substrate, it is assumed that the resulting isotopic enrichment by the tracer will reflect the kinetics of only the pool of interest. However, this may not be the case when carbon-labeled lactate is infused, since rapid isotopic exchange with the intracellular pyruvate and alanine pools could potentially occur. Therefore we have determined the extent of isotopic exchange occurring during the infusion of [3-13C]lactate into six anesthetized dogs. In the steady state, pyruvate enrichment was 91 +/- 2.2% (means +/- SE) of the lactate enrichment, and alanine enrichment was 81 +/- 3.3% of the pyruvate enrichment and 72 +/- 2.6% of the lactate enrichment. In contrast, when [3-13C]alanine was infused (n = 2), pyruvate (and lactate) enrichment was 9.9% of the alanine enrichment. We therefore conclude that there is rapid isotopic equilibration between lactate and pyruvate but that interaction with alanine reflects the true metabolic flux rates, rather than isotopic exchange. Consequently, lactate kinetics, as traditionally determined, more accurately reflect whole body pyruvate kinetics.

Animals↗

PubMed1994

Pyruvate increases threshold for preconditioning in globally ischemic rat hearts.

Isolated rat hearts can be protected by preconditioning, although this has not been found when they are perfused with pyruvate. We addressed the question of whether pyruvate could increase the threshold for preconditioning in isolated rat hearts and whether this could be overcome with increased durations of ischemia. A protocol of four periods of 5 min of ischemic preconditioning (4 x 5 min) protected hearts (improved recovery of function, reduced lactate dehydrogenase release) not perfused with pyruvate from a subsequent 30-min period of global ischemia, but did not protect pyruvate-perfused hearts. Pilot studies indicated that hearts perfused in the presence of pyruvate must be ischemic for approximately 40% longer to produce equivalent ischemic damage in nonpyruvate-treated hearts. Thus the preconditioning period of 5 min was increased by approximately 40% to 7 min to produce equivalent degrees of preconditioning. Hearts preconditioned with the 4 x 7 min protocol with pyruvate were significantly protected against a subsequent severe global ischemia (enhanced recovery of function, reduced lactate dehydrogenase release). High-energy phosphates were measured at the end of the preconditioning protocol (before final global ischemia) to determine whether there was a correlation between cardioprotection and high-energy phosphate levels. There was no correlation between ATP, ADP, or AMP levels and the efficacy of preconditioning. However, an increase in creatine phosphate was associated with cardioprotection, although the importance of this in mediating preconditioning is doubtful. Thus the ability to precondition rat hearts is somewhat dependent on their energy source, but this appears to be due to changes in the severity of the ischemic preconditioning event.

Animals↗