Search PubMed⌕ Search

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.

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

At least 1,423 records · Page 79Linked to original sources
PubMed1973

Physiological role of pyruvate carboxylase in a thermophilic bacillus.

A prototrophic, thermophilic bacillus is in a state of biotin insufficiency when grown in medium consisting of inorganic salts and a carbon source. The effect of this biotin deficiency on the growth rate is severe only if the functioning of pyruvate carboxylase is essential for the utilization of the particular growth substrate. A mutant, PC2, of the thermophile devoid of active pyruvate carboxylase has been isolated. The properties of this mutant confirm the anaplerotic role of this enzyme in the utilization for growth of compounds like glucose and lactate which are catabolized via pyruvate. This conclusion is supported by the finding that revertants isolated from strain PC2 have regained simultaneously the ability to synthesize active pyruvate carboxylase and the ability to utilize glucose or lactate for growth. The growth of mutant PC2 on acetate, unlike that of the parent wild type, is inhibited when glucose or lactate is added to the medium. Secondary mutants obtained from PC2, which are resistant to such inhibition, still carry the original pyruvate carboxylase lesion but are derepressed for isocitrate lyase. This suggests that the inhibition of the growth of mutant PC2 is due to a block in the functioning of the glyoxylate cycle, produced by the glucose or lactate supplement.

Acetates↗
PubMed1974

Pyruvate kinase of Streptococcus lactis.

The kinetic properties of pyruvate kinase (ATP:pyruvate-phosphotransferase, EC 2.7.1.40) from Streptococcus lactis have been investigated. Positive homotropic kinetics were observed with phosphoenolpyruvate and adenosine 5'-diphosphate, resulting in a sigmoid relationship between reaction velocity and substrate concentrations. This relationship was abolished with an excess of the heterotropic effector fructose-1,6-diphosphate, giving a typical Michaelis-Menten relationship. Increasing the concentration of fructose-1,6-diphosphate increased the apparent V(max) values and decreased the K(m) values for both substrates. Catalysis by pyruvate kinase proceeded optimally at pH 6.9 to 7.5 and was markedly inhibited by inorganic phosphate and sulfate ions. Under certain conditions adenosine 5'-triphosphate also caused inhibition. The K(m) values for phosphoenolpyruvate and adenosine 5'-diphosphate in the presence of 2 mM fructose-1,6-diphosphate were 0.17 mM and 1 mM, respectively. The concentration of fructose-1,6-diphosphate giving one-half maximal velocity with 2 mM phosphoenolpyruvate and 5 mM adenosine 5'-diphosphate was 0.07 mM. The intracellular concentrations of these metabolites (0.8 mM phosphoenolpyruvate, 2.4 mM adenosine 5'-diphosphate, and 18 mM fructose-1,6-diphosphate) suggest that the pyruvate kinase in S. lactis approaches maximal activity in exponentially growing cells. The role of pyruvate kinase in the regulation of the glycolytic pathway in lactic streptococci is discussed.

Adenosine Diphosphate↗
PubMed1984

Use of 31P nuclear magnetic resonance spectroscopy and 14C fluorography in studies of glycolysis and regulation of pyruvate kinase in Streptococcus lactis.

High-resolution 31P nuclear magnetic resonance spectroscopy and 14C fluorography have been used to identify and quantitate intermediates of the Embden-Meyerhof pathway in intact cells and cell extracts of Streptococcus lactis. Glycolysing cells contained high levels of fructose 1,6-bisphosphate (a positive effector of pyruvate kinase) but comparatively low concentrations of other glycolytic metabolites. By contrast, starved organisms contained only high levels of 3-phosphoglycerate, 2-phosphoglycerate, and phosphoenolpyruvate. The concentration of Pi (a negative effector of pyruvate kinase) in starved cells was fourfold greater than that maintained by glycolysing cells. The following result suggest that retention of the phosphoenolpyruvate pool by starved cells is a consequence of Pi-mediated inhibition of pyruvate kinase: the increase in the phosphoenolpyruvate pool (and Pi) preceded depletion of fructose 1,6-bisphosphate, and reduction in intracellular Pi (by a maltose-plus-arginine phosphate trap) caused the restoration of pyruvate kinase activity in starved cells. Time course studies showed that Pi was conserved by formation of fructose 1,6-bisphosphate during glycolysis. Conversely, during starvation high levels of Pi were generated concomitant with depletion of intracellular fructose 1,6-bisphosphate. The concentrations of Pi and fructose 1,6-bisphosphate present in starved and glycolysing cells of S. lactis varied inversely. The activity of pyruvate kinase in the growing cell may be modulated by the relative concentrations of the two antagonistic effectors.

Carbon Radioisotopes↗
PubMed1988

Common ancestry of Escherichia coli pyruvate oxidase and the acetohydroxy acid synthases of the branched-chain amino acid biosynthetic pathway.

A number of enzymes require flavin for their catalytic activity, although the reaction catalyzed involves no redox reaction. The best studied of these enigmatic nonredox flavoproteins are the acetohydroxy acid synthases (AHAS), which catalyze early steps in the synthesis of branched-chain amino acids in bacteria, yeasts, and plants. Previously, work from our laboratory showed strong amino acid sequence homology between these enzymes and Escherichia coli pyruvate oxidase, a classical flavoprotein dehydrogenase that catalyzes the decarboxylation of pyruvate to acetate. We have now shown this homology (i) to also be present in the DNA sequences and (ii) to represent functional homology in that pyruvate oxidase has AHAS activity and a protein consisting of the amino-terminal half of pyruvate oxidase and the carboxy-terminal half of E. coli AHAS I allows native E. coli AHAS I to function without added flavin. The hybrid protein contains tightly bound flavin, which is essential for the flavin substitution activity. These data, together with the sequence homologies and identical cofactors and substrates, led us to propose that the AHAS enzymes are descended from pyruvate oxidase (or a similar protein) and, thus, that the flavin requirement of the AHAS enzymes is a vestigial remnant, which may have been conserved to play a structural rather than a chemical function.

Acetolactate Synthase↗
PubMed2006

Pyruvate:quinone oxidoreductase in Corynebacterium glutamicum: molecular analysis of the pqo gene, significance of the enzyme, and phylogenetic aspects.

Corynebacterium glutamicum recently has been shown to possess pyruvate:quinone oxidoreductase (PQO), catalyzing the oxidative decarboxylation of pyruvate to acetate and CO2 with a quinone as the electron acceptor. Here, we analyze the expression of the C. glutamicum pqo gene, investigate the relevance of the PQO enzyme for growth and amino acid production, and perform phylogenetic studies. Expression analyses revealed that transcription of pqo is initiated 45 bp upstream of the translational start site and that it is organized in an operon together with genes encoding a putative metal-activated pyridoxal enzyme and a putative activator protein. Inactivation of the chromosomal pqo gene led to the absence of PQO activity; however, growth and amino acid production were not affected under either condition tested. Introduction of plasmid-bound pqo into a pyruvate dehydrogenase complex-negative C. glutamicum strain partially relieved the growth phenotype of this mutant, indicating that high PQO activity can compensate for the function of the pyruvate dehydrogenase complex. To investigate the distribution of PQO enzymes in prokaryotes and to clarify the relationship between PQO, pyruvate oxidase (POX), and acetohydroxy acid synthase enzymes, we compiled and analyzed the phylogeny of respective proteins deposited in public databases. The analyses revealed a wide distribution of PQOs among prokaryotes, corroborated the hypothesis of a common ancestry of the three enzymes, and led us to propose that the POX enzymes of Lactobacillales were derived from a PQO.

Amino Acids↗
PubMed1969

Role of pyruvate metabolism in the growth of Streptococcus faecalis in the presence of propionate.

The growth of Streptococcus faecalis is inhibited by propionate, and the inhibition is reversed by lipoic acid or acetate. A study of the role of pyruvate oxidation in S. faecalis showed that propionate inhibited the lipoic acid-dependent aerobic oxidation of pyruvate in resting cells. Pyruvate dehydrogenation with neotetrazolium as a hydrogen acceptor in cell-free extracts also required lipoic acid and was markedly inhibited by propionyl phosphate as well as sodium propionate. Some lipid substances, such as palmitate, oleate, behenate, and lecithin, had a lipoic acid-replacing effect on growth of the organism. Biotin or bicarbonate promoted the lipoic acid-dependent growth. Acetate-2-(14)C added to the medium was mainly incorporated into the lipid fraction of the cells. Evolution of (14)CO(2) from pyruvate-2-(14)C was not observed in resting cells of the organism, even under aerobic conditions. From the above findings, it is concluded that lipid synthesis through pyruvate oxidation plays a very important role in bacterial growth in medium containing propionate.

Acetates↗
PubMed1976

Evidence of a novel role for monovalent cations in pyruvate kinase catalysis.

In the pyruvate kinase (EC 2.7.1.40) reaction, the complete enzyme-products complex consists of enzyme, pyruvate, ATP, a divalent cation, and a monovalent cation, usually K+. The dissociation of this complex can be slow permitting reversible enolization of pyruvate in this complex during the course of the forward reaction. High concentrations of each component in the enzyme-products complex inhibits the forward reaction, but only elevated concentrations of the monovalent cation decrease the net rate of product dissociation relative to that of pyruvate enolization. This result indicates that the monovalent cation can be the first component released from the enzyme-products complex and that the presence of an inhibiting monovalent cation concentration leads to re-formation of the complete complex, which is necessary for pyruvate enolization. The evidence suggests that the monovalent cation can bind and release with each turnover of the enzyme. While the data do not permit the conclusion that first release of monovalent cation is the exclusive pathway for dissociation of the enzyme-products complex, no other component once released can reassociate rapidly enough to form a complete complex during the forward reaction. Inhibition by these components must be attributed to the formation of abortive complexes.

Adenosine Triphosphate↗
PubMed1981

L-phenylalanine induced changes of sulfhydryl reactivity in rabbit muscle pyruvate kinase.

Reactivity of sulfhydryl groups in rabbit muscle pyruvate kinase toward 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) was studied in the presence of activating divalent metal ions, substrate, substrate analogue, and the allosteric inhibitor, L-Phe. The pattern of sulfhydryl modification in various complexes of pyruvate kinase was consistent with the extent of enzyme inactivation by DTNB under very similar conditions. The sulfhydryl reactivity of Mg(II)-, Co(II)-, and Mn(II)-substituted pyruvate kinase toward DTNB depended upon the nature of the activating divalent metal ions used in the following order of increasing potency, Mg(II) less than Mn(II) less than Co(II), which is inversely related to the order of catalytic efficiency of these metal ions at alkaline pH. Similar optical spectra and the patterns of sulfhydryl modification by DTNB of the metal derivatives of pyruvate kinase were observed upon the binding of the substrate, phosphoenolpyruvate (PEP), or the substrate analogue, phosphoglycolate, which also provided a complete protection against enzyme inactivation by DTNB. L-PHe, on eht other hand, deprotected the enzyme from inactivation and further sulfhydryl modification by DTNB in the presence of PEP with the following order of potency depending upon the activating metal ions, Mn(II) less than Co(II) less than Mg(II), which parallels the order of metal dependency of L-Phe inhibition of this enzyme. L-Ala, which reverses the L-Phe inhibition of Mg(II)- or Co(II)-activated enzyme, restored the protective effect of PEP in the presence of L-Phe. The different patterns of sulfhydryl reactivity toward Mn(II)-enzyme (hyperbolic) and Mg(II)-enzyme (sigmoidal) correspond well with their kinetic patterns in the presence of L-Phe, indicating the presence of different conformational states between these two metal-enzyme complexes. These results led us to conclude that enzyme sulfhydryl reactivity toward DTNB can be used as a valid index for allosteric conformational changes of rabbit muscles pyruvate kinase.

Alanine↗
PubMed1989

Pyruvate fermentation by Clostridium acetobutylicum.

Clostridium acetobutylicum ATCC 824 using pyruvate as the sole carbon source produced mainly acetate and butyrate as end products of fermentation. Acetate and butyrate kinase activities were higher in cells growing in the presence of pyruvate than glucose, whereas the level of the acetoacetate decarboxylase, an enzyme involved in solvent formation, was lower. Similar activities of glyceraldehyde-3-phosphate dehydrogenase were found in cells grown in pyruvate and glucose mediums. The transfer of C. acetobutylicum from pyruvate to glucose medium suggested that pyruvate represses the "solventogenesis."

Acetate Kinase↗
PubMed1996

Continuous measurement of 13C16O2 production from [13C]pyruvate by intact liver mitochondria: effect of HCO3-.

We have measured continuously the production of mass 45 CO2(13C16O2) from 13C-labeled pyruvate in a guinea pig liver mitochondrial suspension and simultaneously the O2 consumption at 37 degrees C and pH 7.4. The reactions took place in a closed 3-ml volume, stirred, thermoregulated chamber separated from the ion source of a mass spectrometer by a gas-permeable membrane that permitted recording the mass peaks of any gas dissolved in the reaction mixture with a response time as fast as 3 s. If the pyruvate was labeled on C-2, no 13C16O2 was formed, even after 1 h, indicating that C-2 and C-3 were not metabolized in the citric acid cycle. We found that production of 13C16O2 was five times greater in the presence of 25 mM HCO3- than in its absence. A probable mechanism of this CO2/HCO3- effect is carboxylation of pyruvate to oxaloacetate, which would react with acetyl CoA to form citrate and with NADH to form malate, thus removing two major inhibitors of pyruvate dehydrogenase. We conclude that CO2/HCO3- has a potent and hitherto unappreciated regulatory effect on liver pyruvate dehydrogenase.

Animals↗
PubMed1996

Glucose and pyruvate regulate cytokine-induced nitric oxide production by cardiac myocytes.

Metabolic requirements for the production of nitric oxide (NO) by cytokine-stimulated neonatal rat cardiac myocytes (CM) were studied. CM were cultured for 48 h in media containing interleukin-1 beta (IL-1 beta) and free fatty acids. Removal of glucose from the media partially inhibited IL-1 beta-stimulated nitrite (NO2-) production [8.1 +/- 0.3 vs. 4.4 +/- 0.6 nmol.(1.25 X 10(5) cells)-1.48 h-1; P < 0.01; n = 12]. The glycolytic inhibitor 2-deoxy-D-glucose (2-DG) completely inhibited IL-1 beta-stimulated NO2- production [0.7 +/- 0.5 nmol.(1.25 X 10(5) cells)-1.48 h-1; P < 0.01; n = 12]. The addition of the glycolytic end product, pyruvate, completely blocked the 2-DG inhibition of IL-1 beta-stimulated NO2- production [7.4 +/- 0.4 nmol.(1.25 X 10(5) cells)-1.48 h-1; P < 0.01; n = 12]. Pyruvate alone did not significantly enhance NO2- production in the presence or absence of glucose (n = 12). The inactive analogue 3-O-methylglucose had no effect on NO2- production (n = 12). Reverse transcription-polymerase chain reaction revealed that pyruvate blocked 2-DG inhibition of inducible NO synthase mRNA expression. Neither 2-DG nor pyruvate had any effect on GTP-cyclohydrolase I mRNA expression in CM. We report for the first time that optimal IL-1 beta-stimulated NO production by CM requires both glucose and the glycolytic end product pyruvate.

Animals↗
PubMed2000

Protective effect of pyruvate upon cultured mesothelial cells exposed to 2 mM hydrogen peroxide.

Rat peritoneal mesothelial cells in culture have the capability of generating hydrogen peroxide. Exposure of these cells to glucose-enriched, lactated-buffered fluids for peritoneal dialysis significantly increases the production of H(2)O(2). Increased liberation of oxygen radicals also involves the risk of damaging the peritoneal membrane. Pyruvate being a natural oxidant scavenger abundantly present in mammalian cells, we hypothesized that its protective effects facing H(2)O(2) can eventually be of relevance for the mesothelial monolayer of patients on long-term peritoneal dialysis. So far, we designed an experimental study in which rat peritoneal mesothelial cells in culture were exposed to 2 mM H(2)O(2). Cell damage was estimated in terms of decreased capability of the mitochondrial dehydrogenases to reduce MTT. Addition of 2 mM sodium pyruvate to the medium prevented the negative effect of hydrogen peroxide. The MTT/protein values for the control group were 0.00357 +/- 0.00075. The ratio after exposure to 2 mM H(2)O(2) was 0. 00217 +/- 0.00028, whereas that detected in cells incubated in H(2)O(2) plus pyruvate was 0.00325 +/- 0.0082 (p < 0.05). These results indicate that pyruvate protected rat peritoneal mesothelial cells in culture against oxidant injury. These data are one more piece of evidence pointing at pyruvate as a potentially useful buffer for peritoneal dialysis solutions.

Animals↗
PubMedDate not supplied

Attenuation and delay of diabetic cataracts by antioxidants: effectiveness of pyruvate after onset of cataract.

Cataract is one of the most significant vision-impairing complications of diabetes. The present study examined the feasibility of inhibiting cataract formation by treatment with pyruvate, a metabolite known to effectively scavenge reactive species of oxygen and inhibit protein glycation, both known to be involved in the genesis of diabetic cataracts. In addition, pyruvate stimulates tissue metabolism, which is depressed with the onset of cataract formation. The objective of our experiments was to determine if this compound could be effective in offsetting the progress of cataract, specifically if administered after the diabetes-induced lens changes have begun, as opposed to the previous reports wherein it has been reported to delay cataract formation if administered prophylactically with the immediate onset of diabetes. Diabetes was induced by intraperitoneal administration of streptozotocin to mice. Lens transparency was assessed by slit lamp examination and its photography. ATP was determined enzymatically by reacting it with luciferin-luciferase mixture and measuring the fluorescence intensity. The findings described herein are in accordance with this possibility. The incidence of cataract in the group of diabetic animals, where treatment with pyruvate was initiated after the initial lens changes set in, was significantly lower at all times of observation in comparison to the untreated diabetic group. In addition, the severity of opacities in the pyruvate-treated group, when present, was much minor, the transparency of these cases being close to that in the control animals. The ophthalmic findings are supported biochemically by ATP levels, which were significantly higher in the pyruvate group in comparison to the untreated group. The present findings emphasize the clinical usefulness of initiating treatment with anti-oxidants and metabolic agonists even when the lens changes are detected at the time of the diabetes diagnosis. The latter usually comes much later than the onset of visual aberrations. Prophylaxis is not an absolute requirement.

Adenosine Triphosphate↗
PubMed2004

Protection by pyruvate of rat retinal cells against zinc toxicity in vitro, and pressure-induced ischemia in vivo.

PURPOSE: To examine whether zinc accumulation occurs during retinal neuronal death after pressure-induced ischemia in rats and whether pyruvate protects against such death. METHODS: To induce transient retinal ischemia, intraocular pressure was increased above systolic pressure for 65 minutes. Pyruvate was administered through the tail vein for 12 hours after ischemia to determine its effect on degeneration of retinal neurons. Retinas were removed and sectioned, and zinc accumulation was visualized with N-(6-methoxy-8-quinolyul)-p-carboxybenzoyl-sylphonamide (TFL-Zn) fluorescence microscopy, and neuronal death was determined with acid fuchsin staining. For in vitro studies, retinal cell cultures were prepared from newborn rat pups and used for experiments at days in vitro (DIV) 7 to 10. RESULTS: After retinal ischemia, staining revealed that most zinc-accumulating neurons were injured neurons, suggesting that endogenous zinc may contribute to ischemic neuronal death in the retina. In vitro studies showed that 15 minutes of exposure to 300 to 500 microM zinc resulted in the death of a substantial number of retinal cells in culture, and that this death was preceded by poly(ADP-ribose) polymerase (PARP)-mediated depletion of nicotinamide-adenine dinucleotide (NAD+) and adenosine triphosphate (ATP). Pyruvate, but not lactate, protected against this zinc-induced cell death in vitro. Consistent with this finding, in vivo studies showed that compared with control rats, pyruvate-treated rats had a substantial reduction in the number of cells showing signs of cell death. CONCLUSIONS: The present results suggest endogenous zinc contributes to retinal cell death after ischemia. Pyruvate potently protected against zinc toxicity in cultured rat retinal cells and reduced ischemia-induced cell death in rat retinas.

Adenosine Triphosphate↗
PubMed2005

Metabolic cardioprotection by pyruvate: recent progress.

Pyruvate, a natural metabolic fuel and antioxidant in myocardium and other tissues, exerts a variety of cardioprotective actions when provided at supraphysiological concentrations. Pyruvate increases cardiac contractile performance and myocardial energy state, bolsters endogenous antioxidant systems, and protects myocardium from ischemia-reperfusion injury and oxidant stress. This article reviews and discusses basic and clinically oriented research conducted over the last several years that has yielded fundamental information on pyruvate's inotropic and cardioprotective mechanisms. Particular attention is placed on pyruvate's enhancement of sarcoplasmic reticular Ca2+ transport, its antioxidant properties, and its ability to mitigate reversible and irreversible myocardial injury. These research efforts are establishing the essential foundation for clinical application of pyruvate therapy in numerous settings including cardiopulmonary bypass surgery, cardiopulmonary resuscitation, myocardial stunning, and cardiac failure.

Animals↗
PubMed1975

Pyruvate dehydrogenase phosphatase deficiency: a cause of congenital chronic lactic acidosis in infancy.

A male child presented on the first day of life with metabolic acidosis with elevated blood lactate (15 mM), pyruvate (0.4 mM), and free fatty acid (1.3 mM) levels and a blood pH of 7.16. The severity of the acidosis was diminished by intravenous administration of glucose in large doses and by bicarbonate. On two occasions, when the acidosis was particularly severe, peritoneal dialysis using an acetate buffer was required. Restriction of the dietary intake of saturated fatty acids or treatment with nicotinic acid also appeared to diminish the severity of acidosis. No improvement was achieved by the administration of thiamine or biotin. Tissues taken at postmortem showed normal activity of gluconeogenic enzymes and pyruvate dehydrogenase. The activity of pyruvate dehydrogenase in tissue homogenates preincubated with ATP was reduced by 60-75% both in liver of the patient and of the controls because of the inactivation of the enzyme by pyruvate dehydrogenase kinase. Addition of Ca++ and Mg++ to the inactivated enzyme caused a prompt return of the activity to normal in controls but not in the patient. This defect, which was apparent in muscle and liver but not in brain, we attribute to a markedly reduced activity of pyruvate dehydrogenase phosphatase in the patient.

Acidosis↗
PubMed1982

Brain pyruvate carboxylase and the pathophysiology of biotin-dependent diseases.

Given the cerebellar symptomatology of biotin-dependent diseases and other lactic acidoses, we hypothesized that cerebellar pyruvate carboxylase activity might be differentially low or especially sensitive to cofactor deprivation. Accordingly, pyruvate carboxylase activity was measured in selected areas of normal and biotin-deficient rat brain. Control cerebellar hemisphere and vermis specific activities were identical, and slightly higher than cerebral and brainstem activities. In biotin-deficient rats, hepatic pyruvate carboxylase activity was 3% of control, whereas pyruvate carboxylase activities of all brain sections were 53 to 71% of control. Brain histology was normal. Cerebellar pyruvate carboxylase activity is therefore not distinctly low or labile and is in fact preferentially maintained despite severe cofactor deprivation.

Animals↗
PubMed1977

Inactivation of pyruvate kinase type M2 from chicken liver by phosphorylation, catalyzed by a cAMP-independent protein kinase.

A cAMP-independent protein kinase from chicken liver phosphorylated and inactivated pyruvate kinase type M2 from the same tissue. Complete inactivation was reached when 4 mol of phosphate were incorporated/mol of tetrameric pyruvate kinase. The protein kinase bound with high affinity to pyruvate kinase type M2 (Km value for pyruvate kinase = 6 X 10(-10)M; it phosphorylated phosvitin and casein but not histones, ATP and GTP were substrates. The differences between the properties of this protein kinase in the interconversion of pyruvate kinase and that described previously are discussed.

Animals↗