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PubMed1976

Selective modification of rabbit muscle pyruvate kinase by 5-chloro-4-oxopentanoic acid.

Rabbit muscle pyruvate kinase was irreverisbly inactivated by 5-chloro-4-oxopentanoic acid with a pKa of 9.2. The inhibition was time-dependent and was related to the 5-chloro-4-oxopentanoic acid concentration. Analysis of the kinetics of inhibition showed that the binding of the inhibitor showed positive co-operativity (n = 1.5 +/- 0.2). Inhibition of pyruvate kinase by 5-chloro-4-oxopentanoic acid was prevented by ligands which bind to the active site. Their effectiveness was placed in the order Mg2+ greater than phosphoenolpyruvate greater than ATP greater than ADP greater than pyruvate. Inhibitor-modified pyruvate kinase was unable to catalyse the detritiation of [3-(3)H]pyruvate in the ATP-promoted reaction, but it did retain 5-10% of the activity with either phosphate or arsenate as promoters. 5-Chlor-4-oxo-[3,5-(3)H]pentanoic acid was covalently bound to pyruvate kinase and demonstrated a stoicheiometry of 1 mol of inhibitor bound per mol of pyruvate kinase protomer. The incorporation of the inhibitor and the loss of enzyme was proportional. These results are discussed in terms of 5-chloro-4-oxopentanoic acid alkylating a functional group in the phosphoryl overlap region of the active site, and a model is presented in which this compound alkylates an active-site thiol in a reaction that is controlled by a more basic group at the active site.

Alkylation↗
PubMed2003

Eubacterium pyruvativorans sp. nov., a novel non-saccharolytic anaerobe from the rumen that ferments pyruvate and amino acids, forms caproate and utilizes acetate and propionate.

Two similar gram-positive rods were isolated from 10(-6) dilutions of ruminal fluid from a sheep receiving a mixed grass hay/concentrate diet, using a medium containing pancreatic casein hydrolysate as sole source of carbon and energy. The isolates did not ferment sugars, but grew on pyruvate or trypticase, forming caproate as the main fermentation product and valerate to a lesser extent. Acetate and propionate were utilized. One of these strains, I-6T, was selected for further study. Strain I-6T was a non-motile coccal rod, 1.2 x 0.4 microm, with a gram-positive cell wall ultrastructure and a G + C content of 56.8 mol%. No spores were visible, and strain I-6T did not survive heating at 80 degrees C for 10 min. Its rate of NH3 production was 375 nmol (mg protein)(-1) min(-1), placing it in the 'ammonia-hyperproducing' (or HAP) group of ruminal bacteria. 16S rDNA sequence analysis (1296 bases) indicated that it represents a novel species within the 'low-G + C' gram-positive group, for which the name Eubacterium pyruvativorans sp. nov. is proposed. Among cultivated bacteria, strain I-6T was most closely related (89% identity) to other asaccharolytic Eubacterium isolates from the mouth and the rumen. It was 98% identical to uncultured bacterial sequences amplified by others from ruminal digesta.

Acetic Acid↗
PubMedDate not supplied

[Role of pyruvate dehydrogenase and ATP-citrate (pro-3S)lyase in inhibition of the biosynthesis of fatty acids by nicotinic acid].

The pyruvate dehydrogenase and ATP-citrate(pro-3S)lyase activity in the liver after administration of nicotinic acid to chickens against a background of stimulated lypogenesis is shown to increase in the period of maximum fall of the acetyl-CoA-carboxylase activity. Affinity of ATP-citrate (pro-3S)-lyase to citrate at this time is lowered, the content of citrate and isocitrate is elevated and CoASac is decreased to some extent. A conclusion is made on the absence of substrate limitation of acetyl-CoA-carboxylase with administration of nicotinic acid to chickens under conditions of the fatty acid biosynthesis intensification.

ATP Citrate (pro-S)-Lyase↗
PubMed2006

Biochemical stress response in freshwater fish Channa punctatus induced by aqueous extracts of Euphorbia tirucalli plant.

Piscicidal activities of aqueous extracts of Euphorbia tirucalli were very well established, but their ultimate mode of action on fish metabolism was not yet known. Exposure of fishes over 24h or 96h to sub-lethal doses (40% and 80% of LC(50)) of aqueous extract of E. tirucalli stem-bark and latex, significantly (P<0.05) altered the level of total protein, total free amino acids, nucleic acids, glycogen, pyruvate, lactate and activity of protease, alanine aminotransferase, aspartate aminotransferase, acetylcholinesterase and cytochrome oxidase enzyme in liver and muscle tissues of freshwater fish Channa punctatus. The alterations in all these biochemical parameters were significantly (P<0.05) time- and dose-dependent. After 7d of withdrawal of treatment of 80% of LC(50) of E. tirucalli extracts shows that there was a partial recovery in the levels of glycogen but nearly complete recovery in total protein, total free amino acids, pyruvate, lactate, nucleic acids level and activity of protease, aspartate aminotransferase, alanine aminotransferase, acetylcholinesterase and cytochrome oxidase enzyme in both the tissues of fish. Thus aqueous extracts of E. tirucalli adversely affect respiratory pathway of fish and cause energy crisis during stress by suppressing ATP production. The reversibility of the action of the aqueous extracts would be an additional advantage in their use.

Acetylcholinesterase↗
PubMed1985

Phorbol ester provokes insulin-like effects on glucose transport, amino acid uptake, and pyruvate dehydrogenase activity in BC3H-1 cultured myocytes.

We evaluated the possibility that diacylglycerol may function as a second messenger in insulin action. To this end, we employed 12-O-tetradecanoyl phorbol 13-acetate (TPA) to mimic diacylglycerol in BC3H-1 myocytes. Like insulin, TPA provoked rapid increases in 2-deoxyglucose transport and pyruvate dehydrogenase activity in mature insulin-responsive BC3H-1 cultured myocytes. TPA also stimulated amino acid uptake, as evidenced by uptake of alpha-methylaminoisobutyric acid; the relatively slow time course of this effect paralleled that of insulin. In contrast, the effects of TPA were not apparent in undifferentiated BC3H-1 myoblasts, which were also unresponsive to insulin. The insulin-like effects in the myocytes appeared to be specific for TPA, the biologically active phorbol diester which activates protein kinase C, as other tested phorbol derivatives were without effect. Effects of maximally effective concentrations of TPA and insulin were nonadditive. Two synthetic diacylglycerols, 1,2-diolien and 1-oleoyl-2-acetyl-sn-glycerol, also provoked insulin-like effects on 2-deoxyglucose transport. Since insulin rapidly increases diacylglycerol levels in these cells, and TPA mimics diacylglycerol biochemically, it is possible that insulin may control cellular processes through changes in diacylglycerol.

Amino Acids↗
PubMed1999

Indole-3-pyruvic and -propionic acids, kynurenic acid, and related metabolites as luminophores and free-radical scavengers.

Chemiluminescence associated with oxidation by free radicals was investigated in an alkaline, hemin-catalysed hydrogen peroxide system, using the following tryptophan metabolites as radical scavengers: indole-3-pyruvic, indole-3-propionic, kynurenic, xanthurenic and quinaldic acids and 4-hydroxy-quinoline. Light emission from oxidation of the indolic compounds was only partially inhibited by the hydroxyl-radical scavenger DMSO, but strongly suppressed by the superoxide-anion scavenger Tiron, whereas chemi-luminescence generated from kynurenic acid was strongly inhibited by either of these compounds. Light emission from oxidation of kynurenic acid lasts for a surprisingly long period of time: At 0.4 mM and 20 degrees C, luminescence increased for 5 hours and continued at a high rate for more than a day. Comparison of structural analogues indicated that the 4-hydroxyl and carboxyl groups of kynurenic acid are essential for effective light emission, and that an additional 8-hydroxyl residue leading to an intramolecular hydrogen bond diminishes the reaction rate.

Dimethyl Sulfoxide↗
PubMed1976

Cerebral blood flow and exchange of oxygen, glucose, ketone bodies, lactate, pyruvate and amino acids in infants.

Cerebral blood flow (CBF) and cerebral av-differences of oxygen and circulating substrates were measured in normocapnic infants during general anaesthesia before elective surgery in order to study possible age-dependent variations. CBF was determined by a minor modification of the Kety-Schmidt technique from desaturation curves of nitrous oxide (N2O) in arterial and cerebral venous blood (N2O analysed by gas chromatography on 15 mul blood samples) after reduction of inhaled N2O from 75 to 50%. The reproducibility was +/-4.6%. Lactate, pyruvate and oxygen were determined in whole blood and amino acids in plasma by ion-exchange chromatography. Reliable av-differences of glucose, acetoacetate and D-beta-hydroxybutyrate could be calculated from plasma values and hematocrits. Mean values from 12 infants (age 11 days-12 months) were: CBF 69 ml/100 g0min-1; cerebral uptake (in mumoles/100 g-min-1): oxygen 104, glucose 27, acetoacetate 0.9, D-beta-hydroxybutyrate 2.3; cerebral release: lactate 2.4 and pyruvate 0.8. Significant uptake of amino acids was found only for histidine 0.95 and arginine 0.7. Significant correlations between arterial concentration and cerebral exchange were found for: ornithine, arginine, phenylalanine, aspartic acid, serine, glutamine and acetoacetate. CBF and substrate exchange were unrelated to age within the group. Infants had higher mean CBF and greater uptake of ketone bodies than has been reported in adults.

Acetoacetates↗
PubMed1997

In situ nucleic acid hybridization of pyruvate dehydrogenase complex-E2 in primary biliary cirrhosis: pyruvate dehydrogenase complex-E2 messenger RNA is expressed in hepatocytes but not in biliary epithelium.

Pyruvate dehydrogenase-E2, or a cross-reactive molecule, has been shown by a variety of immunohistochemical methods to be present in increased amounts in biliary epithelial cells (BEC) in primary biliary cirrhosis (PBC). In this study, to further understand the nature of the immunoreactive molecule in BEC, we examined the expression of pyruvate dehydrogenase complex-E2 (PDC-E2) messenger RNA (mRNA) and PDC-E2 protein in sections of livers from patients and controls to help identify the molecule found in BEC. We performed in situ hybridization using an antisense probe against the major epitope of PDC-E2. The data were very striking and suggested that there was no increased production of PDC-E2 in BEC. For example, in livers from patients with PBC, PDC-E2 mRNA was found in periportal hepatocytes in 16 of 17 cases (94%). In contrast, interlobular bile ducts and septal bile ducts had detectable levels of PDC-E2 mRNA in only 1 of 17 (6%) and 3 of 8 (38%) cases, respectively. Interestingly, proliferating bile ductules contained detectable levels of mRNA in 12 of 15 cases (80%). In control liver, periportal hepatocytes were positive in 15 of 17 cases (88%). Interlobular bile ducts, septal bile ducts, and proliferating bile ductules expressed mRNA signals in 4 of 17 (24%), 2 of 10 (20%), and 14 of 16 (88%), respectively. When formalin-fixed, paraffin-embedded sections were examined by immunohistochemical staining with anti-PDC-E2 monoclonal antibody (mAb) C355.1, the interlobular bile ducts showed typical aberrant apical staining in all 10 PBC cases, but 0 of 9 liver controls. Periportal hepatocytes, proliferating bile ductules and infiltrating mononuclear cells stained with C355.1 but in a characteristic mitochondrial staining pattern. The presence of a PDC-E2-like molecule recognized by C355.1 is not reflected by the expression levels of PDC-E2 mRNA in the BEC of patients with PBC.

Bile Ducts↗
PubMed1995

Utilization of short-chain monocarboxylic acids by the yeast Torulaspora delbrueckii: specificity of the transport systems and their regulation.

Cells of Torulaspora delbrueckii IGC 4478 grown in a medium with DL-lactic acid (0.5% v/v, at pH 5.0) exhibited Michaelis-Menten kinetics for labelled L-lactic acid transport with the following parameters at pH 5.0: Vmax, 0.38 nmol of total L-lactic acid s-1 per mg dry weight of cells and Km, 0.05 mM total L-lactic acid. Furthermore, evidence was available indicating that a proton symport for the charged form of the acid was involved. D-lactic, acetic, propionic, pyruvic and formic acids were competitive inhibitors of labelled L-lactic acid transport, suggesting that these acids used the same transport system. The ability of T. delbrueckii IGC 4478 to grow with acetic acid as the carbon source was dependent on the acid concentration and on the pH of the culture medium. When the cells were grown in 0.5% (v/v) acetic acid (pH 6.0), the transport of labelled acetic acid followed a Michaelis-Menten kinetics with the following parameters at pH 5.0: Vmax, 2.93 nmol of total acetic acid s-1 per mg dry weight of cells and and Km, 0.55 mM total acetic acid. The system also displayed a behavior consistent with a proton symport mechanism. However, the specificity of this carrier was distinct from that observed for the monocarboxylate transport in DL-lactic acid grown cells. While propionic and formic acids were competitive inhibitors of the labelled acetic acid transport, DL-lactic and pyruvic acids did not exhibit any inhibitory effects on that transport. Moreover, under the same conditions, no uptake was observed when the transport was measured with labelled L-lactic acid. Both systems were inducible and subjected to repression by glucose, fructose or sucrose. Accordingly, diauxic growth was observed in a medium containing a mixture of any of these sugars plus lactic pyruvic or acetic acid. While the induction of the acetate proton-symport appeared to be exclusively associated with acetic acid, the lactate proton-symport could be induced by either lactic or pyruvic acid but not by acetic acid. Besides, glucose repressed cells were still permeable to the undissociated form of the acids which entered the cells by simple diffusion. Furthermore, the activities of the lactate proton-symport and of the acetate proton-symport appeared not to be associated with the activity of the L-lactate (cytochrome) dehydrogenase.

Acetates↗