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PubMed1984

[Lactate and pyruvate metabolism in the tissues of rats with Walker carcinosarcoma injected with oxythiamine].

The levels of L-lactate and pyruvate as well as the enzymes of their conversion (lactate dehydrogenase in direct and reverse reactions, pyruvate dehydrogenase, pyruvate kinase, alanine transaminase) have been studied simultaneously in the liver and skeletal muscle of rats bearing carcinosarcoma Walker 256, control animals and after additional oxythiamine administration. Properties of oxythiamine independent of its anticoenzymic activity manifest themselves in the body of tumour-bearing animals to a greater extent. After the antivitamin administration there occur strong inhibition of pyruvate kinase, activation of alanine transaminase, normalization of the L-lactate level in the tissues.

Alanine Transaminase↗
PubMed1980

Pyruvate dehydrogenase activity in group N streptococci.

Pyruvate dehydrogenase activity was detected in whole cells but not in cell-free extracts of Streptococcus lactis. However, the three component enzymes (pyruvate decarboxylase, lipoate acetyltransferase and lipoyl dehydrogenase) of the pyruvate dehydrogenase complex were identified in the cell-free extracts. Whole cells of the three species of group N streptococci formed acetoin and diacetyl only after the pathway forming acetate had become saturated. S. lactis subsp. diacetylactis DRC2 formed more acetoin and diacetyl and less acetate from pyruvate than did S. lactis C10. Strains C10 and DRC2 were able to form acetoin via alpha-acetolactate or diacetyl and to convert acetoin to butane-2,3-diol. S. cremoris HP was able to form acetoin only via alpha-acetolactate and could not convert acetoin to butane-2,3-diol.

Acetyltransferases↗
PubMed1993

[Spectroscopic study of the structure and intramolecular mobility of yeast pyruvate decarboxylase].

Steady-state and time-resolved fluorimetry were used to study the properties of holo- and apopyruvate decarboxylase (EC 4.1.1.1, PDC) from Brewer's yeast after interaction with substrate (pyruvate), cofactor (thiamine diphosphate, ThDP) and Mg2+ ions. The analysis of the enzyme's intrinsic fluorescence as well as of its complex with the probe 2-(p-toluidinylnaphthalene)-6-sulphonate (TNS) revealed that ThDP was found at the polar region of the PDC active sites, inducing a decrease in the mobility of the protein's nearest surroundings. The fluorescent probe had three different sites of binding to the protein apoform, two of which being located at the catalytic site and having different rotation freedom. The study of the PDC complex with thiochrome pyrophosphate, a ThDP structural analogue, pointed to the occurrence of a non-polar region of the enzyme active site for pyruvate absorption besides the polar region. The binding of pyruvate to the protein does not depend upon the cofactor's binding. On the basis of the fluorescent studies a model of the ThDP and pyruvate arrangement at the PDC active site is suggested.

Anilino Naphthalenesulfonates↗
PubMed1993

Influence of pyruvate, threonine and phosphoethanolamine on activities of some acetaldehyde-producing enzymes.

Threonine (50 mg/100 g, i.p.) leads to increased hepatic threonine aldolase activity in rats, although endogenous ethanol concentrations remain stable. After pyruvate administration (50 mg/100 g, i.p.), endogenous blood ethanol levels are raised within 30 min, but return to normal at 60 min. The activity of threonine aldolase is decreased in the liver, whereas phosphoethanolamine lyase and pyruvate dehydrogenase activities remain unchanged. Phosphoethanolamine administration (23 mg/100 g, i.p.) did not change the endogenous ethanol concentration or pyruvate dehydrogenase, threonine aldolase and phosphoethanolamine lyase activities. Pyruvate appears to be a better precursor of acetaldehyde than threonine or phosphoethanolamine.

Acetaldehyde↗
PubMed1996

Cloning and expression of a rat kidney cytosolic glutamine transaminase K that has strong sequence homology to kynurenine pyruvate aminotransferase.

An alpha-keto acid-dependent cysteine S-conjugate beta-lyase of rat kidney was identified as cytosolic glutamine transaminase K by Stevens et al. (J. Biol. Chem. 261, 15529-15537, 1986). Subsequently, a rat kidney protein with both glutamine transaminase K- and cysteine S-conjugate beta-lyase activities was cloned and sequenced by Perry et al. (Mol. Pharmacol. 43, 660-665, 1993). This protein was later shown to be identical with kynurenine pyruvate aminotransferase (Mosca et al., FEBS Lett. 353, 21-24, 1994). Thus, kynurenine pyruvate aminotransferase possesses both glutamine transaminase K- and cysteine S-conjugate beta-lyase-type activities. We have also cloned a cytosolic glutamine transaminase K from a rat kidney cDNA library and expressed the full-length clone in COS1 cells. The transfected cells exhibit marked increases in activities of both glutamine transaminase K and cysteine S-conjugate beta-lyase. The enzyme cloned in the present work is a homodimer. Each subunit has a molecular mass of 45.8 kDa and contains 426 amino acid residues. The sequence of cytosolic glutamine transaminase K obtained in the present work has strong similarities to other aminotransferases, including >90% identity with kynurenine pyruvate aminotransferase. Our preparation of purified rat kidney cytosolic glutamine transaminase K possesses some kynurenine pyruvate aminotransferase activity. Thus, rat kidney cytosol possesses at least two distinct enzymes that catalyze glutamine transaminase K/cysteine S-conjugate beta-lyase/kynurenine pyruvate aminotransferase reactions. The present work underscores the difficulties associated with characterizing aminotransferases with overlapping specificities.

Amino Acid Sequence↗
PubMed1990

Pyruvate:NADP+ oxidoreductase from Euglena gracilis: mechanism of O2-inactivation of the enzyme and its stability in the aerobe.

O2-inactivation of pyruvate:NADP+ oxidoreductase from mitochondria of Euglena gracilis was studied in vitro, and a mechanism which consists of two sequential stages was proposed. Initially, the enzyme is inactivated by the direct action of O2 in a process obeying second-order kinetics. Although the catalytic activity for pyruvate oxidation is lost by this initial inactivation, NADPH oxidation with artificial electron acceptors still occurs. Subsequently, a secondary, O2-independent inactivation occurs, rendering the enzyme completely inactive. Pyruvate stimulates the O2-inactivation while CoA and NADP+ protect the enzyme from O2. The O2-inactivation is accelerated by reduction of the enzyme with pyruvate and CoA. Reactivation of the O2-inactivated enzyme was studied in Ar by incubation with Fe2+ in the presence of some other reducing reagent such as dithiothreitol. The evidence obtained indicates that the partially inactivated enzyme, which retains catalytic activity for NADPH oxidation, can be reactivated, but the completely inactivated enzyme is not. When Euglena cells were exposed to 100% O2 the enzyme in the cells was inactivated by O2, but the rate was quite slow compared with that observed in vitro. The enzyme inactivated by O2 in the cells was almost completely reactivated in vitro by incubation with Fe2+ and other reducing reagents in Ar, suggesting that the secondary, O2-independent inactivation does not occur in situ. When the cells were returned to air, reactivation of the O2-inactivated enzyme in the cells began immediately. The enzyme, kept in isolated, intact mitochondria, was stable in air; however, the enzyme was inactivated by O2 when the mitochondria were incubated with a high concentration of pyruvate.

Animals↗
PubMed2002

Bifidobacteria identification based on 16S rRNA and pyruvate kinase partial gene sequence analysis.

The lack of a simple and rapid identification system for Bifidobacterium species makes them difficult to use in industrial applications. To obtain valuable discriminating factor, we studied different strains, and human isolates by two molecular taxonomy methods. First method was based on chrono-differentiation. A metabolic gene (pyruvate kinase) was chosen to be used as a systematic discriminating factor. A comparison of about 40 pyruvate kinase protein sequences allowed us to synthesize two oligonucleotides that were able to amplify a fragment of this corresponding gene in our strains. Based on these partial pyruvate kinase gene sequences, several clusters could be identified. The second method used in this study was based on 16S rRNA sequences analysis. We compared sequences present in GenBank database, and this allowed to separate bifidobacteria species into different clusters. They were different from those obtained with partial pyruvate kinase gene sequences analysis. So, by combining both methods, we were able to identify our isolates, when only 10% of them could be strictly identified using the 16S rRNA method. Moreover, pyruvate kinase analysis allowed to differentiate very ambivalent groups such as B. animalis/B. lactis or B. infantis/B. longum, but created different clusters for B. infantis species group, questioning on the homogeneity of this species.

Journal Article↗
PubMed1973

Effect of phenylpyruvate on pyruvate dehydrogenase activity in rat brain mitochondria.

1. The effects of phenylpyruvate, a metabolite produced in phenylketonuria, on the pyruvate dehydrogenase-complex activity were investigated in rat brain mitochondria. 2. Pyruvate dehydrogenase activity was measured by two methods, one measuring the release of (14)CO(2) from [1-(14)C]pyruvate and the other measuring the acetyl-CoA formed by means of the coupling enzyme, pigeon liver arylamine acetyltransferase (EC 2.3.1.5). In neither case was there significant inhibition of the pyruvate dehydrogenase complex by phenylpyruvate at concentrations below 2mm. 3. However, phenylpyruvate acted as a classical competitive inhibitor of the coupling enzyme arylamine acetyltransferase, with a K(i) of 100mum. 4. It was concluded that the inhibition of pyruvate dehydrogenase by phenylpyruvate is unlikely to be a primary enzyme defect in phenylketonuria.

Journal Article↗
PubMed1980

Crystallization and characterization of human liver kynurenine--glyoxylate aminotransferase. Identity with alanine--glyoxylate aminotransferase and serine--pyruvate aminotransferase.

Kynurenine-glyoxylate aminotransferase, alanine-glyoxylate aminotransferase and serine-pyruvate aminotransferase were co-purified and crystallized as yellow cubes from human liver particulate fraction. The crystalline enzyme was homogeneous by the criteria of electrophoresis, isoelectric focusing, gel filtration, sucrose-density-gradient centrifugation and analytical ultracentrifugation. The molecular weight of the enzyme was calculated as approx. 90000, 89000 and 99000 by the use of gel filtration, analytical ultracentrifugation and sucrose-density-gradient centrifugation respectively, with two identical subunits. The enzyme has a s(20,w) value of 5.23S, an isoelectric point of 8.3 and a pH optimum between 9.0 and 9.5. The enzyme solution showed absorption maxima at 280 and 420nm. The enzyme catalysed transamination between several l-amino acids and pyruvate or glyoxylate. The order of effectiveness of amino acids was alanine>serine>glutamine>glutamate>methionine>kynurenine = phenylalanine = asparagine>valine>histidine>lysine>leucine>isoleucine>arginine>tyrosine = threonine>aspartate, with glyoxylate as amino acceptor. The enzyme was active with glyoxylate, oxaloacetate, hydroxypyruvate, pyruvate, 4-methylthio-2-oxobutyrate and 2-oxobutyrate, but showed little activity with phenylpyruvate, 2-oxoglutarate and 2-oxoadipate, with kynurenine as amino donor. Kynurenine-glyoxylate aminotransferase activity was competitively inhibited by the addition of l-alanine or l-serine. From these results we conclude that kynurenine-glyoxylate aminotransferase, alanine-glyoxylate aminotransferase and serine-pyruvate aminotransferase activities of human liver are catalysed by a single protein. Kinetic parameters for the kynurenine-glyoxylate aminotransferase, alanine-glyoxylate aminotransferase, serine-pyruvate aminotransferase and alanine-hydroxypyruvate aminotransferase reactions of the enzyme are presented.

Aged↗
PubMed1984

Binding specificity of serum amyloid P component for the pyruvate acetal of galactose.

Serum amyloid P component (SAP) is a normal plasma protein that is of interest because of its presence in amyloid deposits, its presence in normal human glomerular basement membrane, and its stable evolutionary conservation. It has calcium-dependent ligand-binding specificity for amyloid fibrils, fibronectin (Fn), C4-binding protein (C4bp), and agarose. Although the binding to agarose, a linear galactan hydrocolloid derived from some marine algae, is unlikely per se to be related to the physiological function of SAP, it does provide a model system in which to explore the precise ligand requirements of SAP. We report here that the amount of SAP from human, mouse, and plaice (Pleuronectes platessa L.) serum able to bind to agarose from different sources reflect precisely their pyruvate content. Methylation with diazomethane of the carboxyl groups in the pyruvate moiety of agarose completely abolishes SAP binding to agarose. The pyruvate in agarose exists as the 4,6-pyruvate acetal of beta-D-galactopyranose. We have therefore synthesized this galactoside, using a novel procedure, established its structure by analysis of its nuclear magnetic resonance spectra, and shown that it completely inhibits all known calcium-dependent binding reactions of SAP. The R isomer of the cyclic acetal, methyl 4,6-O-(1-carboxyethylidene)-beta-D-galactopyranoside (MO beta DG) was effective at millimolar concentration and was more potent than its noncyclic analogue, while pyruvate, D-galactose, and methyl beta-D-galactopyranoside were without effect. The autologous protein ligands of SAP presumably, therefore express a structural determinant(s) that stereochemically resembles MO beta DG. Availability of this specific, well-characterized, low molecular weight ligand for SAP should facilitate further investigation of the function of SAP and its role in physiological and pathophysiological processes.

Amyloid↗
PubMed1984

Uptake and processing of serine: pyruvate aminotransferase precursor by rat liver mitochondria in vitro and in vivo.

Processing and uptake of the precursor of serine: pyruvate aminotransferase [EC 2.6.1.51] by mitochondria were studied in vitro and in vivo. Serine: pyruvate aminotransferase was synthesized mainly on free ribosomes as judged by immunoprecipitation of puromycin-labeled nascent peptides prepared from free and bound ribosomes. The precursor of rat liver serine:pyruvate aminotransferase (pSPT) synthesized in vitro was post-translationally processed to an apparently mature form by isolated rat liver mitochondria. Available evidence indicated that the processed product was localized in the matrix of mitochondria. Mature serine:pyruvate aminotransferase did not inhibit the in vitro processing, suggesting that the extra peptide was necessary for the mitochondrial uptake of the precursor. In the livers of rats fed a vitamin B6-deficient high-protein diet, the induction by glucagon of serine:pyruvate aminotransferase occurred and most of the induced enzyme existed in mitochondria as the apo-form, suggesting that pSPT was taken up by mitochondria and processed in the apo-form under the conditions employed. In the in vitro system, on the other hand, the processing of pSPT proceeded both in the absence and presence of pyridoxal 5'-phosphate. Should the precursor also bind the prosthetic molecule, therefore, it would be transported into mitochondria in both the apo- and holo-forms. When isolated rat hepatocytes were labeled with [35S]methionine, labeled pSPT appeared in the cytosolic fraction and was transported rapidly into mitochondria in association with the processing. This uptake and processing were inhibited by a fluorescent laser dye, rhodamine 123, and the precursor accumulated in the cytosol in the presence of the dye.

Animals↗
PubMed1993

Monovalent Cation Activation of Plant Pyruvate Dehydrogenase Kinase.

The pyruvate dehydrogenase kinase-catalyzed inactivation of the pyruvate dehydrogenase complex was studied using dialyzed, soluble proteins from mitochondria purified from green leaf tissue of Pisum sativum L. seedlings. At subsaturating ATP concentrations, K+ or NH4+, but not Na+, stimulated the pyruvate dehydrogenase kinase by lowering the Km(ATP). Micromolar concentrations of NH4+ were required to produce the same effect as millimolar concentrations of K+. This is apparent from the observations that the activation constant (Kact) for NH4+ was 0.1 mM, whereas the Kact(K+) was 0.7 mM. Maximal pyruvate dehydrogenase kinase velocities attained with NH4+ were higher than those with K+, and, therefore, NH4+ was able to stimulate PDH kinase further in the presence of saturating K+. This result supports our conclusion that photorespiratory NH4+ production in plant mitochondria may be involved in regulating the entry of carbon into the Krebs cycle by way of the pyruvate dehydrogenase complex.

Journal Article↗
PubMed1976

Regulation of malate oxidation in isolated mung bean mitochondria: I. Effects of oxaloacetate, pyruvate, and thiamine pyrophosphate.

In order to investigate the relationship between malate oxidation and subsequent cycle reactions, the effects of oxaloacetate, pyruvate, and thiamine pyrophosphate on malate oxidation in mung bean (Phaseolus aureus var. Jumbo) hypocotyl mitochondria were quantitatively examined. Malate oxidation was optimally stimulated by addition of pyruvate and thiamine pyrophosphate, whose addition lowered the apparent Km for malate from 5 mm to 0.1 mm. Intermediate analysis showed that the stimulatory effect was correlated with removal of oxaloacetate to citrate. Oxaloacetate added alone was shown not to be metabolized until addition of pyruvate and thiamine pyrophosphate; then oxaloacetate was converted in part to pyruvate and also to citrate. These results establish that malate oxidation in mung bean mitochondria is subject to control by oxaloacetate levels, which are primarily determined by the resultant of the activities of malate dehydrogenase, citrate synthase, and pyruvate dehydrogenase.

Journal Article↗
PubMed1978

Properties of pyruvate kinase from soybean nodule cytosol.

The properties of pyruvate kinase from soybean (Glycine max L.) nodule cytosol were examined to determine what influence the N(2) fixation process might have on this supposed key control enzyme. A crude enzyme preparation was prepared by chromatography of cytosol extract on a diethylaminoethyl-cellulose column. ATP and citrate at 5 mm concentrations inhibited pyruvate kinase 27 and 34%, respectively. Enzyme activation was hyperbolic with respect to both K(+) and NH(4) (+) concentrations. In the presence of physiological concentrations of K(+) and high phosphoenolpyruvate (PEP) concentrations, NH(4) (+) inhibited enzyme activity. Comparisons of kinetic parameters (V(max) and apparent K(a)) for NH(4) (+) and K(+) with inhibition curves indicated that inhibition was very likely a result of competition of the ions for activation site(s) on the pyruvate kinase. In addition, apparent K(a) (monovalent cation) and K(m) (PEP) were influenced by PEP and monovalent cation concentrations, respectively. This effect may reflect a fundamental difference between plant and animal pyruvate kinases. It is concluded that control of cytosol pyruvate kinase may be closely related to reactions involved in the assimilation of NH(4) (+).

Journal Article↗
PubMed1983

Carbon dioxide effects on ethanol production, pyruvate decarboxylase, and alcohol dehydrogenase activities in anaerobic sweet potato roots.

The effect of varied anaerobic atmospheres on the metabolism of sweet potato (Ipomoea batatas [L.] Lam.) roots was studied. The internal gas atmospheres of storage roots changed rapidly when the roots were submerged under water. O(2) and N(2) gases disappeared quickly and were replaced by CO(2). There were no appreciable differences in gas composition among the four cultivars that were studied. Under different anaerobic conditions, ethanol concentration in the roots was highest in a CO(2) environment, followed by submergence and a N(2) environment in all the cultivars except one. A positive relationship was found between ethanol production and pyruvate decarboxylase activity from both 100% CO(2)-treated and 100% N(2)-treated roots. CO(2) atmospheres also resulted in higher pyruvate decarboxylase activity than did N(2) atmospheres. Concentrations of CO(2) were higher within anaerobic roots than those in the ambient anaerobic atmosphere. The level of pyruvate decarboxylase and ethanol in anaerobic roots was proportional to the ambient CO(2) concentration. The measurable activity of pyruvate decarboxylase that was present in the roots was about 100 times less than that of alcohol dehydrogenase. Considering these observations, it is suggested that the rate-limiting enzyme for ethanol biosynthesis in sweet potato storage roots under anoxia is likely to be pyruvate decarboxylase rather than alcohol dehydrogenase.

Journal Article↗
PubMed1983

Influence of Oxygen and Temperature on the Dark Inactivation of Pyruvate, Orthophosphate Dikinase and NADP-Malate Dehydrogenase in Maize.

The influence of oxygen and temperature on the inactivation of pyruvate, Pi dikinase and NADP-malate dehydrogenase was studied in Zea mays. O(2) was required for inactivation of both pyruvate, Pi dikinase and NADP-malate dehydrogenase in the dark in vivo. The rate of inactivation under 2% O(2) was only slightly lower than that at 21% O(2). The in vitro inactivation of pyruvate, Pi dikinase, while dependent on adenine nucleotides (ADP + ATP), did not require O(2).The postillumination inactivation of pyruvate, Pi dikinase in leaves was strongly dependent on temperature. As temperature was decreased in the dark, there was a lag period of increasing length (e.g. at 17 degrees C there was a lag of about 25 minutes) before inactivation proceeded. Following the lag period, the rate of inactivation decreased with decreasing temperature. The half-time for dark inactivation was about 7 minutes at 32 degrees C and 45 minutes at 17 degrees C. The inactivation of pyruvate, Pi dikinase in vitro following extraction from illuminated leaves was also strongly dependent on temperature, but occurred without a lag period. In contrast, NADP-malate dehydrogenase was rapidly inactivated in leaves (half-time of approximately 3 minutes) during the postillumination period without a lag, and there was little effect of temperature between 10 and 32 degrees C. The results are discussed in relation to known differences in the mechanism of activation/inactivation of the two enzymes.

Journal Article↗
PubMed1985

Anaerobic Formation of d-Lactate and Partial Purification and Characterization of a Pyruvate Reductase from Chlamydomonas reinhardtii.

d-Lactate accumulation in Chlamydomonas reinhardtii was dependent on anaerobic conditions. As much as 50% of the (14)C after 2 minutes of photosynthetic (14)CO(2) fixation moved into d-lactate from sugar phosphates if the cells became anaerobic for short time periods. No lactate accumulated in the dark until the O(2) concentration decreased to less than 0.1%. Lactate was determined to be of the d-configuration using stereospecific lactate dehydrogenases. d-Lactate produced anaerobically by algae grown on 5% CO(2) was only slowly metabolized aerobically in the light or dark, and in the dark, only a trace of the lactate was excreted.A pyruvate reductase (d-lactate: diphosphopyridine nucleotide oxidoreductase, EC 1.1.1.28) was partially purified 47-fold from Chlamydomonas. Because this enzyme catalyzes an essentially irreversible reaction in the direction of pyruvate reduction, it is considered to be a pyruvate reductase. The reductase activity in extracts of Chlamydomonas was 30 micromoles per hour per milligram chlorophyll. For the partially purified enzyme, the apparent K(m) (pyruvate) was 0.5 millimolar, and the pH optimum was 7.0. Studies with cycloheximide and chloramphenicol indicated that the enzyme was constitutive in aerobic cells. Potassium phosphate stimulated the reductase, and high salt and dithiothreitol were required for stability. The enzyme demonstrated substrate inhibition and was inhibited by ATP. Pyruvate reductase was separated from a hydroxypyruvate reductase by gel filtration chromatography, indicating the presence of separate reductases for these two substrates in Chlamydomonas.

Journal Article↗
PubMed1992

Malate- and pyruvate-dependent Fatty Acid synthesis in leucoplasts from developing castor endosperm.

Leucoplasts were isolated from the endosperm of developing castor (Ricinis communis) endosperm using a discontinuous Percoll gradient. The rate of fatty acid synthesis was highest when malate was the precursor, at 155 nanomoles acetyl-CoA equivalents per milligram protein per hour. Pyruvate and acetate also were precursors of fatty acid synthesis, but the rates were approximately 4.5 and 120 times less, respectively, than when malate was the precursor. When acetate was supplied to leucoplasts, exogenous ATP, NADH, and NADPH were required to obtain maximal rates of fatty acid synthesis. In contrast, the incorporation of malate and pyruvate into fatty acids did not require a supply of exogenous reductant. Further, the incorporation of radiolabel into fatty acids by leucoplasts supplied with radiolabeled malate, pyruvate, or acetate was reduced upon coincubation with cold pyruvate or malate. The data suggest that malate and pyruvate may be good in vivo sources of carbon for fatty acid synthesis and that, in these preparations, leucoplast fatty acid synthesis may be limited by activity at or downstream of the acetyl-CoA carboxylase reaction.

Journal Article↗