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PubMed1970

The intracellular localization of enzymes in white-adipose-tissue fat-cells and permeability properties of fat-cell mitochondria. Transfer of acetyl units and reducing power between mitochondria and cytoplasm.

1. A method is described for extracting separately mitochondrial and extramitochondrial enzymes from fat-cells prepared by collagenase digestion from rat epididymal fat-pads. The following distribution of enzymes has been observed (with the total activities of the enzymes as units/mg of fat-cell DNA at 25 degrees C given in parenthesis). Exclusively mitochondrial enzymes: glutamate dehydrogenase (1.8), NAD-isocitrate dehydrogenase (0.5), citrate synthase (5.2), pyruvate carboxylase (3.0); exclusively extramitochondrial enzymes: glucose 6-phosphate dehydrogenase (5.8), 6-phosphogluconate dehydrogenase (5.2), NADP-malate dehydrogenase (11.0), ATP-citrate lyase (5.1); enzymes present in both mitochondrial and extramitochondrial compartments: NADP-isocitrate dehydrogenase (3.7), NAD-malate dehydrogenase (330), aconitate hydratase (1.1), carnitine acetyltransferase (0.4), acetyl-CoA synthetase (1.0), aspartate aminotransferase (1.7), alanine aminotransferase (6.1). The mean DNA content of eight preparations of fat-cells was 109mug/g dry weight of cells. 2. Mitochondria showing respiratory control ratios of 3-6 with pyruvate, about 3 with succinate and P/O ratios of approaching 3 and 2 respectively have been isolated from fat-cells. From studies of rates of oxygen uptake and of swelling in iso-osmotic solutions of ammonium salts, it is concluded that fat-cell mitochondria are permeable to the monocarboxylic acids, pyruvate and acetate; that in the presence of phosphate they are permeable to malate and succinate and to a lesser extent oxaloacetate but not fumarate; and that in the presence of both malate and phosphate they are permeable to citrate, isocitrate and 2-oxoglutarate. In addition, isolated fat-cell mitochondria have been found to oxidize acetyl l-carnitine and, slowly, l-glycerol 3-phosphate. 3. It is concluded that the major means of transport of acetyl units into the cytoplasm for fatty acid synthesis is as citrate. Extensive transport as glutamate, 2-oxoglutarate and isocitrate, as acetate and as acetyl l-carnitine appears to be ruled out by the low activities of mitochondrial aconitate hydratase, mitochondrial acetyl-CoA hydrolyase and carnitine acetyltransferase respectively. Pathways whereby oxaloacetate generated in the cytoplasm during fatty acid synthesis by ATP-citrate lyase may be returned to mitochondria for further citrate synthesis are discussed. 4. It is also concluded that fat-cells contain pathways that will allow the excess of reducing power formed in the cytoplasm when adipose tissue is incubated in glucose and insulin to be transferred to mitochondria as l-glycerol 3-phosphate or malate. When adipose tissue is incubated in pyruvate alone, reducing power for fatty acid, l-glycerol 3-phosphate and lactate formation may be transferred to the cytoplasm as citrate and malate.

Acetates↗
PubMed1986

Metabolism of exercising skeletal muscle during beta 1-selective adrenoceptor blockade.

Concentrations of glycogen, glucose, glucose-6-phosphate and lactate in the lateral vastus muscle were measured in seven subjects before and after dynamic muscle exercise at a work load of 75% of each subject's maximal working capacity, and with and without intravenous administration of the beta 1-selective beta-adrenoceptor blocking agent, atenolol. Pulmonary oxygen uptake was measured during exercise. Heart rate and arterial blood pressure were measured throughout the study. Arterial concentrations of glucose, lactate and free fatty acids were measured at rest and during exercise. The muscle concentration of glycogen and the extent of glycogen depletion with exercise were not influenced by the beta 1-adrenoceptor blocker. Similarly, there was no change in the muscle concentrations of glucose, glucose-6-phosphate and lactate. Heart rate decreased at rest and during exercise. Arterial blood pressure was not influenced by beta-blockade. Pulmonary oxygen uptake decreased by 6.5%. The exercise induced rise in arterial blood concentration of free fatty acids was abolished by beta 1-selective beta-blockade. It is concluded that the decrease in lactate release from exercising muscles during beta 1-adrenoceptor blockade seen in other studies cannot be explained by an impaired breakdown of muscle glycogen. It may be inferred, however, that a reduced availability of free fatty acids in the exercising muscles during beta 1-selective (and non-selective) beta-blockade may enhance the combustion of pyruvic acid and thereby decrease the production of lactate.

Adult↗
PubMedDate not supplied

[Effect of malonate on various aspects of hepatic metabolism].

Malonate was tested for its effects on rat hepatic metabolism of [1,4-14C]-succinic acid and [1-14C]-glycerol. The administration of malonic acid did not limit [1,4-14C]-succinate metabolism and change the rate of radioactive labelling from [1-14C]-glycerol to the total lipid fraction, as well as the fraction of phospholipids and triacylglycerides. However, there was a reduction in the use of glycerol as a precursor of higher fatty acids and cholesterol. It is suggested that the detected effect of malonate is due to its action on oxidative decarboxylation of pyruvic acid.

Animals↗
PubMed1996

Effects of the methyl esters of pyruvate, succinate and glutamate on the secretory response to meglitinide analogues in rat pancreatic islets.

The insulinotropic action of the meglitinide analogues KAD-1229, A-4166 and repaglinide was examined in rat pancreatic islets deprived of exogenous nutrient or incubated in the presence of nutrient secretagogues such as D-glucose and the methyl esters of pyruvic acid, succinic acid and glutamic acid. The meglitinide analogues exerted little effect on insulin release in the absence of exogenous nutrient or in the presence of methyl pyruvate. They caused obvious stimulation of insulin output in the presence of D-glucose, dimethyl succinate or dimethyl glutamate. It is proposed, therefore, that suitable esters of dicarboxylic nutrients could be used to potentiate the secretory response to meglitinide analogues in non-insulin-dependent diabetes mellitus.

Animals↗
PubMed1984

Novel formation of alpha-amino acids from alpha-oxo acids and ammonia in an aqueous medium.

In the course of a study of possible mechanisms for chemical evolution in the primeval sea, we found the novel formation of alpha-amino acids and N-acylamino acids from alpha-oxo acids and ammonia in an aqueous medium. Glyoxylic acid reacted with ammonia to form N-oxalylglycine, which gave glycine in a 5-39% yield after hydrolysis with 6N HC1. Pyruvic acid and ammonia reacted to give N-acetylalanine, which formed alanine in a 3-7% overall yield upon hydrolysis. The pH optima in these reactions were between pH 3 and 4. These reactions were further extended to the formation of other amino acids. Glutamic acid, phenylalanine and alanine were formed from alpha-ketoglutaric acid, phenylpyruvic acid and oxaloacetic acid, respectively, under similar conditions. N-Succinylglutamic acid was obtained as an intermediate in glutamic acid synthesis. Phenylacetylphenylalanineamide was also isolated as an intermediate in phenylalanine synthesis. Alanine, rather than aspartic acid, was produced from oxaloacetic acid. These reactions provide a novel route for the prebiotic synthesis of amino acids. A mechanism for the reactions will be proposed.

Amino Acids↗
PubMed1983

Effect of sodium glycolate and sodium pyruvate on oxalic acid biosynthesizing enzymes in rat liver and kidney.

Sodium glycolate feeding (50 mg/100 g body weight/day) to adult male rats for 7 days resulted in increased activities of glycolate oxidase in liver and lactate dehydrogenase in liver and kidney. However, the activity of glycolate dehydrogenase decreased both in liver and kidney. Treatment of sodium pyruvate (100 mg/100 g body weight/day) to the glycolate-fed rats resulted in lowered liver glycolate oxidase activity, and the glycolate dehydrogenase activity was further decreased as compared to glycolate-fed rats in both age groups. However, lactate dehydrogenase activity was not affected by pyruvate feeding in comparison to the glycolate-treated group. It is concluded that glycolate-induced oxalate biosynthesis in rats involves increased activity of liver glycolate oxidase, and pyruvate feeding inhibits glycolate oxidase, thereby decreasing oxalate biosynthesis.

Alcohol Oxidoreductases↗
PubMed1977

Cellular content of the Krebs cycle keto acids in yeasts grown on different nitrogen sources, including hydroxylamine.

The cellular pool of Krebs cycle keto acids was followed as a function of growth in three yeasts. The keto acids were analyzed as silylated methoximes by quantitative gas chromatography with capillary glass columns. The 2-oxoglutaric acid content was strikingly high in the hydroxylamine (HA)-tolerant, HA-utilizing Endomycopsis lipolytica when compared to that in the nitrate-utilizing yeast Cryptococcus albidus and Saccharomyces cerevisiae, requiring fully reduced nitrogen for growth. The content of E. lipolytica increased throughout the log phase to maxima of about 200-250 microgram per g dry weight in HA and ammonia media. These amounts are 20-25 times greater than those attained in the two other yeasts. The cellular content of pyruvic acid was at a maximum early in the log phase, amounting to 50-70 microgram per g dry weight for all yeasts. The oxalacetic acid content never exceeded 9 microgram per g dry weight in any of the yeasts. Oximeformation, for which keto acid production is a prerequisite, is discussed as part of the HA-tolerance.

Ammonium Sulfate↗
PubMed1983

A novel way for the formation of alpha-amino acids and their derivatives in an aqueous medium.

In the course of a study of possible mechanism for chemical evolution in the primeval sea, we observed the formation of alpha-amino acids and N-acylamino acids from alpha-oxo acids and ammonia in an aqueous medium. Glyoxylic acid reacted with ammonia to form N-oxalylglycine, which gave glycine in a 5-39% yield after hydrolysis with 6N HCl. Similarly when glyoxylic acid was treated with methylamine it yielded N-oxalylsarcosine, which could be hydrolyzed to sarcosine with 17-25% overall yield upon hydrolysis. Pyruvic acid and ammonia reacted to give N-acetylalanine, which formed alanine in a 3-7% overall yield upon hydrolysis. The pH optima in these reactions were pH 3-4. These reactions were further extended to the formation of other amino acids. Glutamic acid, phenylalanine and serine were formed from alpha-ketoglutaric acid, phenylpyruvic acid and hydroxypyruvic acid, respectively, under similar conditions. N-Succinylglutamic acid was obtained as an intermediate for glutamic acid synthesis. Phenylacetylphenylalanineamide was also isolated as an intermediate for phenylalanine synthesis. Alanine, rather than aspartic acid, was produced from oxaloacetic acid. These reactions provide a novel route for the prebiotic synthesis of amino acids. A mechanism for the reactions is proposed.

Amino Acids↗
PubMed1998

Indole-3-acetic acid biosynthesis in colletotrichum gloeosporioides f. sp. aeschynomene

We characterized the biosynthesis of indole-3-acetic acid by the mycoherbicide Colletotrichum gloeosporioides f. sp. aeschynomene. Auxin production was tryptophan dependent. Compounds from the indole-3-acetamide and indole-3-pyruvic acid pathways were detected in culture filtrates. Feeding experiments and in vitro assay confirmed the presence of both pathways. Indole-3-acetamide was the major pathway utilized by the fungus to produce indole-3-acetic acid in culture.

Journal Article↗
PubMed1992

Tissue lipids in experimental calcium oxalate lithiasis and the effect of DL alpha-lipoic acid.

The function of DL alpha-lipoic acid (6,8-thioctic acid) as a prosthetic group in the oxidative decarboxylation of alpha-keto acids, pyruvate and alpha-ketoglutarate in mitochondria is well known. Its role is well extended to certain reactions in lipid biosynthesis. In addition, lipoic acid has been shown to prevent the induced precipitation of calcium oxalate crystals in the renal tissues of laboratory animals. Here, the effect of alpha-lipoic acid was studied, on altered tissue lipid levels manifested during experimental renal lithiasis. Raised tissue cholesterol, triglyceride and low phospholipid levels were some of the striking significant observations made in calculogenic rats. Lipoic acid treatment reduced tissue cholesterol and triglyceride levels significantly and raised phospholipids. The alterations may have a bearing in relation to calcium oxalate stone formation.

Animals↗
PubMed1965

Metabolism of poly-beta-hydroxybutyrate and acetoin in Bacillus cereus.

Kominek, Leo A. (University of Illinois, Urbana), and H. Orin Halvorson. Metabolism of poly-beta-hydroxybutyrate and acetoin in Bacillus cereus. J. Bacteriol. 90:1251-1259. 1965.-The synthesis of poly-beta-hydroxybutyrate (PHB) in Bacillus cereus strain T begins after the cessation of logarithmic growth. Its accumulation is preceded by the formation of acetoacetyl coenzyme A reductase, an enzyme used for its biosynthesis. Exogenous acetic acid present in the medium owing to incomplete glucose oxidation serves as the carbon source for polymer formation during the initial stages of its synthesis. Pyruvic acid is converted to acetoin by an enzyme system that is formed during vegetative growth. The formation of this enzyme system is dependent on a low pH in the medium. As the cells enter the sporulating stage, they lose the ability to form acetoin. The acetoin that accumulates is utilized via the 2,3-butanediol cycle which begins to function late in the sporulation stage. This cycle generates acetic acid which is used for PHB synthesis and is also oxidized to carbon dioxide. PHB accumulation reaches a maximum just prior to the formation of spores, and it is degraded during the process of sporulation. The effect of sporulation inhibitors and pH on PHB and acetoin metabolism are discussed.

Alcohol Oxidoreductases↗
PubMed1988

Measurement of urinary lactic, 3-hydroxybutyric, pyruvic and acetoacetic acids in a single analysis using selected ion monitoring and stable isotope labelling techniques.

Sodium borodeuteride treatment of urine expected to have large concentrations of pyruvic and acetoacetic acids produces lactic and 3-hydroxybutyric acids labelled with deuterium. Mass fragmentographic techniques applied to the trimethylsilyated extract of the urine spiked with more extensively labelled analogues as internal standards permit the reliable determination of lactic, pyruvic, 3-hydroxybutyric and acetoacetic acids in a single analysis.

3-Hydroxybutyric Acid↗
PubMed2005

Biosynthesis of auxin by the gram-positive phytopathogen Rhodococcus fascians is controlled by compounds specific to infected plant tissues.

The role and metabolism of indole-3-acetic acid in gram-negative bacteria is well documented, but little is known about indole-3-acetic acid biosynthesis and regulation in gram-positive bacteria. The phytopathogen Rhodococcus fascians, a gram-positive organism, incites diverse developmental alterations, such as leafy galls, on a wide range of plants. Phenotypic analysis of a leafy gall suggests that auxin may play an important role in the development of the symptoms. We show here for the first time that R. fascians produces and secretes the auxin indole-3-acetic acid. Interestingly, whereas noninfected-tobacco extracts have no effect, indole-3-acetic acid synthesis is highly induced in the presence of infected-tobacco extracts when tryptophan is not limiting. Indole-3-acetic acid production by a plasmid-free strain shows that the biosynthetic genes are located on the bacterial chromosome, although plasmid-encoded genes contribute to the kinetics and regulation of indole-3-acetic acid biosynthesis. The indole-3-acetic acid intermediates present in bacterial cells and secreted into the growth media show that the main biosynthetic route used by R. fascians is the indole-3-pyruvic acid pathway with a possible rate-limiting role for indole-3-ethanol. The relationship between indole-3-acetic acid production and the symptoms induced by R. fascians is discussed.

Indoleacetic Acids↗
PubMed1966

Chemical degradation of dipicolinic acid-C14 and its application in biosynthesis by Penicillium citreo-viride.

Kanie, Matuso (Kagoshima University, Kagoshima, Japan), Shigeo Fujimoto, and J. W. Foster. Chemical degradation of dipicolinic acid-C(14) and its application to biosynthesis by Penicillium citreo-viride. J. Bacteriol. 91:570-577. 1966.-A chemical degradation of dipicolinic acid-C(14) has been worked out, enabling determination of the specific radioactivity of the carboxyl-carbons (carbons-7 and -8), and of the following carbons of the pyridine ring: carbons-2 and -6 combined, carbons-3 and -5 combined, and carbon-4. The degradation was applied to dipicolinic acid synthesized by washed, submerged mycelium of the mold from glucose and C(14)O(2), and from glucose-1-C(14), -2-C(14), and -6-C(14). The distribution of radioactivity within the labeled dipicolinic acids is consistent with operation of respiratory cycles and with the incorporation of one molecule of CO(2) in the pyridine acid. A C(3) compound is a primary building block. The C(7) chain is believed to result from a C(3) plus C(4) condensation, pyruvic acid and aspartic acid beta-semialdehyde being proposed as likely precursors. Other aspects of the biosynthesis of C(7) open-chain compounds and of dipicolinic acid are discussed.

Carbon Dioxide↗
PubMed1976

Spin-label study of the mobility of enzyme-bound lipoic acid in the pyruvate dehydrogenase multienzyme complex of Escherichia coli.

The lipoic acid residues covalently bound to the transacetylase component of the pyruvate dehydrogenase multienzyme complex of Escherichia coli were selectively modified by reaction with 4-maleimido-2,2,6,6-tetramethylpiperidino-oxyl. The electron-spin-resonance spectrum of the spin-labelled enzyme indicates that the bound nitroxide groups have high mobilities relative to the protein molecule. This physicochemical evidence is consistent with the view that the dithiolane ring of a lipoyl residue is capable of rapid migration between the active sites of the component enzymes in the catalytic mechanism.

Escherichia coli↗
PubMed1979

Structural studies of the capsular polysaccharide of Klebsiella type 33.

The structure of the capsular polysaccharide from Klebsiella type 33 has been investigated. Methylation analysis, various specific degradations, graded hydrolysis with acid, and n.m.r. spectroscopy were the principal methods used. It is concluded that the polysaccharide is composed of pentasaccharide repeating-units having the following structure. (formula, see manual). The D-galactopyranosyl group, with pyruvic acid linked as a ketal to O-3 AND O-4, was degraded on treatment of the fully methylated polysaccharide with strong base. It is proposed that methyl pyruvate is eliminated, in an E2 type of reaction.

Chemical Phenomena↗
PubMed1999

Biosynthesis of indole-3-acetic acid in Azospirillum brasilense. Insights from quantum chemistry.

Quantum chemical methods AM1 and PM3 and chromatographic methods were used to qualitatively characterize pathways of bacterial production of indole-3-acetic acid (IAA). The standard free energy changes (delta G(o)'sum) for the synthesis of tryptophan (Trp) from chorismic acid via anthranilic acid and indole were calculated, as were those for several possible pathways for the synthesis of IAA from Trp, namely via indole-3-acetamide (IAM), indole-3-pyruvic acid (IPyA), and indole-3-acetonitrile (IAN). The delta G(o)'sum for Trp synthesis from chorismic acid was -402 (-434) kJ.mol-1 (values in parentheses were calculated by PM3). The delta G(o)'sum for IAA synthesis from Trp were -565 (-548) kJ.mol-1 for the IAN pathway, -481 (-506) kJ.mol-1 for the IAM pathway, and -289 (-306) kJ.mol-1 for the IPyA pathway. By HPLC analysis, the possibility was assessed that indole, anthranilic acid, and Trp might be utilized as precursors for IAA synthesis by Azospirillum brasilense strain Sp 245. The results indicate that there is a high motive force for Trp synthesis from chorismic acid and for IAA synthesis from Trp, and make it unlikely that anthranilic acid and indole act as the precursors to IAA in a Trp-independent pathway.

Azospirillum brasilense↗