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At least 1,315 records · Page 73Linked to original sources
PubMed1984

Mechanism of L-malate transport in rat renal basolateral membrane vesicles.

The transport of L-malate was evaluated in basolateral and brush border membrane vesicles isolated from the rat renal cortex. In both types of membrane vesicles, an inwardly directed sodium gradient stimulated transport and caused an overshoot of the equilibrium concentration. In basolateral membrane vesicles, the presence of sodium, but without a sodium gradient, stimulated the uptake of L-malate. Sodium gradient-stimulated L-malate uptake was stimulated and inhibited by maneuvers designed to render the inside of the basolateral membrane vesicles more electronegative or electropositive, respectively. The tricarboxylic acid cycle intermediates citrate, alpha-ketoglutarate, succinate, fumarate, L-malate, and oxaloacetate and the monocarboxylic acid pyruvate inhibited the sodium gradient-stimulated uptake of L-[14C]malate in basolateral membrane vesicles. Maleate, gluconate, formate, acetate, L-lactate, and beta-hydroxybutyrate did not inhibit uptake. These results indicate that basolateral membrane vesicles from the rat renal cortex contain a sodium-L-malate cotransport system that may be shared by the other tricarboxylic acid cycle intermediates and by pyruvate. Such a transport system, together with a similar sodium-tricarboxylic acid cycle intermediate cotransport system located in the brush border membrane, would ensure high concentrations of tricarboxylic acid cycle intermediates within the cells of the proximal tubule.

Animals↗
PubMed1998

Phosphate starvation-independent 2-aminoethylphosphonic acid biodegradation in a newly isolated strain of Pseudomonas putida, NG2.

A strain of Pseudomonas putida that utilized the biogenic organophosphonate 2-aminoethylphosphonic acid as sole carbon and energy, nitrogen and phosphorus source contained 2-aminoethylphosphonic acid: pyruvate aminotransferase and phosphonoacetaldehyde hydrolase (phosphonatase) activities which were inducible by the presence of 2-aminoethylphosphonic acid in the culture medium, regardless of the phosphate status of the cells. Neither of these activities were induced in their phosphate-free or phosphate-replete medium in the absence of 2-aminoethylphosphonic acid. Alkaline phosphatase activity was induced in phosphate limited medium, however, indicating a phosphate-starvation inducible response. In Enterobacter aerogenes IFO 12010, 2-aminoethylphosphonate: pyruvate aminotransferase and phosphonatase activities were induced only when cells were both phosphate limited and supplied with 2-aminoethylphosphonic acid as sole phosphorus source for growth. Neither enzyme activity was induced in phosphate-replete medium, or in medium where both 2-aminoethylphosphonic acid and inorganic phosphate were supplied as sources of phosphorus. The results point to the presence of a substrate inducible 2-aminoethylphosphonic acid biodegradation pathway in the isolated strain of Pseudomonas putida. Uniquely, therefore, the pathway is not under pho regulon control in this strain.

Alkaline Phosphatase↗
PubMed1992

Effects of dentin surface treatments on the shear bond strength of Vitrabond.

The influences of nine dentin surface treatments were evaluated on the shear bond strength of a new light-cured glass-ionomer cement (GIC) and on the SEM morphology of the treated dentin surfaces. The following treatments were performed: saline solution (control), NaOCl, acidic glycine, EDTA, malic acid, malic acid plus glycine, polyacrylic acid, tannic acid, and neutral+acidic oxalate solutions. Buccal dentin surfaces were polished with #320-grit abrasive paper, treated with one of the chemicals, washed, and air-dried. Cylindrical GIC samples were then applied to the dentin surface, stored in 100% humidity, and tested after 24 h. SEM observations demonstrated no effect of saline or NaOCl treatment on the smear layer but its complete removal with exposure of collagen fibrils after malic or malic acid plus glycine treatment. Partial removal of the smear layer occurred following glycine treatment and with tannic or polyacrylic acids. Complete removal of the smear layer was seen after EDTA or pyruvic acid treatment. Oxalate treatment produced a layer of crystals, which completely covered the dentin surface. Shear bond strength of GIC was significantly increased only by treatment with the oxalate solutions.

Dental Bonding↗
PubMed1999

Effect of amino acids on the plasma concentration and urinary excretion of uric acid and uridine.

To determine the effect of amino acids on the plasma level and urinary excretion of uric acid and uridine, 200 mL 12% amino acid solution, and 2 weeks later, 100 mL physiological saline solution containing glucagon (1.2 microg/kg weight), was infused into five healthy men. Both increased the urinary excretion of uric acid and the concentration of glucagon, insulin, and glucose in plasma and pyruvic acid in blood, whereas they decreased the concentration of uridine and inorganic phosphate in plasma. However, neither the amino acid infusion nor glucagon infusion affected the concentration of purine bases (hypoxanthine, xanthine, and uric acid), cyclic adenosine monophosphate (cAMP) in plasma, or lactic acid in blood or the urinary excretion of oxypurines (hypoxanthine and xanthine), uridine, or sodium. These results suggest that glucagon may have an important role in the amino acid-induced increase in urinary excretion of uric acid and decrease in plasma uridine.

Adult↗
PubMed1963

EFFECT OF PH ON INTERMEDIATES PRODUCED DURING GROWTH AND SPORULATION OF BACILLUS CEREUS.

Nakata, H. M. (Washington State University, Pullman). Effect of pH on intermediates produced during growth and sporulation of Bacillus cereus. J. Bacteriol. 86:577-581. 1963.-Cultures of Bacillus cereus strain T, grown in an unbuffered glucose-yeast extract-mineral salts medium and in the same medium buffered at pH 6.4, 7.0, or 7.4, were examined to determine the effect of pH on the production and utilization of metabolic intermediates during growth and sporulation. Although the growth rate of the unbuffered cultures decreased as a result of changes in pH, the growth rates of the buffered cultures were constant and similar. Only slight differences were observed in the final number of spores produced, and in the time required for the completion of the sporulation process. Acetic and lactic acids were the chief acidic end products of growth in buffered media, in which more than twice the amount of these acids accumulated than was detected in unbuffered cultures. In the latter cultures, pyruvic acid, rather than lactic acid, was formed together with acetate. Acetoin also accumulated in the unbuffered cultures, but none was detected in any of the buffered cultures. All of these intermediates were rapidly utilized by the cells once sporulation began. Poly-beta-hydroxybutyric acid accumulation in the cells during the early stages of sporulation was also influenced by pH, with the greatest accumulation of this polymer occurring in the cells grown at pH 6.2 to 6.4. These results support the hypothesis that high polymer content in the cells is not imperative for the completion of sporulation. However, if any is formed, it is completely utilized during the final stages of spore formation.

Acetates↗
PubMedDate not supplied

[Metabolic effects of succinic and nicotinic acids in emotional pain stress].

In experiments on rats it was shown that administration of succinic and nicotinic acids in doses of 30 and 4 mg/kg for 5 days elevated pyruvic acid level and changed catecholamine balance in tissues of the aorta and heart. The administration of the drugs to rats with current-induced stress partially eliminated unfavourable shifts in carbohydrate metabolism and catecholamine balance in the aortic and cardiac tissues. Succinic acid had more pronounced metabolic activity.

Adrenal Glands↗
PubMed1979

Production of S-sulfocysteine from so-called cystine disulfoxide in the presence of aspartate aminotransferase.

S-Sulfocysteine production occurred when so-called cystine disulfoxide was incubated with aspartate aminotransferase and 2-oxoglutarate. Evidence was provided indicating that the alanine sulfinic acid portion of cystine disulfoxide was transaminated and the resulting sulfinylpyruvic acid portion decomposed non-enzymatically to give S-sulfocysteine and pyruvic acid.

Aspartate Aminotransferases↗
PubMed2000

Azospirillum, a free-living nitrogen-fixing bacterium closely associated with grasses: genetic, biochemical and ecological aspects.

Azospirillum represents the best characterized genus of plant growth-promoting rhizobacteria. Other free-living diazotrophs repeatedly detected in association with plant roots, include Acetobacter diazotrophicus, Herbaspirillum seropedicae, Azoarcus spp. and Azotobacter. Four aspects of the Azospirillum-plant root interaction are highlighted: natural habitat, plant root interaction, nitrogen fixation and biosynthesis of plant growth hormones. Each of these aspects is dealt with in a comparative way. Azospirilla are predominantly surface-colonizing bacteria, whereas A. diazotrophicus, H. seropedicae and Azoarcus sp. are endophytic diazotrophs. The attachment of Azospirillum cells to plant roots occurs in two steps. The polar flagellum, of which the flagellin was shown to be a glycoprotein, mediates the adsorption step. An as yet unidentified surface polysaccharide is believed to be essential in the subsequent anchoring phase. In Azoarcus sp. the attachment process is mediated by type IV pili. Nitrogen fixation structural genes (nif) are highly conserved among all nitrogen-fixing bacteria, and in all diazotrophic species of the class of proteobacteria examined, the transcriptional activator NifA is required for expression of other nif genes in response to two major environmental signals (oxygen and fixed N). However, the mechanisms involved in this control can vary in different organisms. In Azospirillum brasilense and H. seropedicae (alpha- and beta-subgroup, respectively), NifA is inactive in conditions of excess nitrogen. Activation of NifA upon removal of fixed N seems to involve, either directly or indirectly, the signal transduction protein P(II). The presence of four conserved cysteine residues in the NifA protein might be an indication that NifA is directly sensitive to oxygen. In Azotobacter vinelandii (gamma-subgroup) nifA is cotranscribed with a second gene nifL. The nifL gene product inactivates NifA in response to high oxygen tension and cellular nitrogen-status. NifL was found to be a redox-sensitive flavoprotein. The relief of NifL inhibition on NifA activity, in response to N-limitation, is suggested to involve a P(II)-like protein. Moreover, nitrogenase activity is regulated according to the intracellular nitrogen and O(2) level. In A. brasilense and Azospirillum lipoferum posttranslational control of nitrogenase, in response to ammonium and anaerobiosis, involves ADP-ribosylation of the nitrogenase iron protein, mediated by the enzymes DraT and DraG. At least three pathways for indole-3-acetic acid (IAA) biosynthesis in A. brasilense exist: two Trp-dependent (the indole-3-pyruvic acid and presumably the indole-3-acetamide pathway) and one Trp-independent pathway. The occurrence of an IAA biosynthetic pathway not using Trp (tryptophan) as precursor is highly unusual in bacteria. Nevertheless, the indole-3-pyruvate decarboxylase encoding ipdC gene is crucial in the overall IAA biosynthesis in Azospirillum. A number of genes essential for Trp production have been isolated in A. brasilense, including trpE(G) which codes for anthranilate synthase, the key enzyme in Trp biosynthesis. The relevance of each of these four aspects for plant growth promotion by Azospirillum is discussed.

Anthranilate Synthase↗
PubMed1979

Acquired pyruvate kinase deficiency. The effect of maleic acid upon human erythrocyte pyruvate kinase.

1. Maleic acid is shown to be able to bind the thiol compound 2-mercaptoethanol. This is fully consistent with the data of Morgan and Friedman (1938). 2. Human erythrocyte pyruvate kinase dissolved and quantitated in Tris-maleate shows a loss of positive homotropic interactions, as compared to the same preparation in Tris-HCl. Hill coefficients (n) of n = 1.0-1.2 and n = 1.6-1.8 are obtained in Tris-maleate and Tris-HCl respectively. Half saturation [S] 0.5 and Vmax remain unchanged. Pyruvate kinase in Tris-maleate is slightly more stable to heating at 60 degrees C than in Tris-HCl. Incubation of the enzyme in Tris-maleate for one h with high concentrations of dithiotreitol restores the positive homotropic interactions. 3. It is proposed, that the abnormalities of the pyruvate kinase of some patients with acquired pyruvate kinase deficiency, obtained from a study in Tris-maleate, may partly be induced by the buffer itself.

Erythrocytes↗
PubMed1979

Development of a chemically defined liquid medium for growth of Legionella pneumophila.

A chemically defined liquid medium has been developed for the study of the physiology and antigen production of the Legionnaires disease bacterium. The medium contains basal salts, vitamins, alpha-ketoglutaric acid, pyruvate, 0.05% l-cysteine, 0.05% glutathione, and a mixture of 20 additional amino acids, each of 0.01% final concentration, except serine, which was at 0.1%. The medium in shake culture at 37 degrees C with increased CO2 at pH 6.5, supports the maximum rate of growth, the highest cell yields, and the maximum cell surface antigen as distinguished by specific fluorescein isothiocyanate-conjugated antibody. Studies during the development of this medium showed that CO2, pyruvate, and alpha-ketoglutarate strongly stimulated growth; that cysteine and methionine were required for growth; and that serine, threonine, histidine, tyrosine, and tryptophane were energy sources. Glutathione substituted for cysteine, but cystine did not. The organisms did not use glucose and polysaccharides, as judged by cell yields when these carbohydrates were present or absent. The chelators malate, citrate, and ethylenediaminetetraacetic acid totally inhibited growth. Beta-mercaptoethanol, thioglycolate, dithiothreitol, and Tween 80 (0.05%) inhibited growth strongly or completely. Catalase activity was extremely weak or absent. Morphology varied, depending upon conditions and phases of growth. In general, filamentous forms became chains of cigar-shaped bacilli fragmenting to pairs and becoming coccoidal in the late stationary pha-e of growth. The organism grew at 25, 30, and 37 degrees C. Although they varied in their growth characteristics, 10 isolates were passed for five transfers in the chemically defined broth, giving maximum rates of growth, cell yields, and antigen production.

Aerobiosis↗
PubMed1984

A study of blood ascorbic acid in leprosy.

The basal level of blood ascorbic acid was studied in 70 cases of polar leprosy. The level was found to be significantly reduced in both polar types, more so in tuberculoid. In untreated cases of these two polar forms, the differences were highly significant. No significant differences were found between untreated and treated cases of either form of leprosy, indicating that dapsone (DDS) has no effect on the ascorbic acid level. In lepromatous leprosy, the level was not affected by erythema nodosum leprosum (ENL). The deficiency of ascorbic acid in leprosy might be due to the disease per se and/or associated with nutritional factors. In trophic ulcers after supplement therapy for 60 days, the low level of ascorbic acid became close to the control group with marked improvement in the healing of the ulcers clinically. In addition, lactic and pyruvic acids were also measured and found to be significantly raised. After ascorbic acid supplement, the levels fell to near the control values, indicating that ascorbic acid played a role in controlling the infection as well as possible thiamine deficiency and also checked the disturbance caused by DDS on lactate and pyruvate metabolism. The present study suggested that supplementing DDS therapy with ascorbic acid might provide a beneficial effect on the general condition of the leprosy patients and the early healing of trophic ulcers.

Ascorbic Acid↗
PubMed2004

Functional characterization of an aminotransferase required for pyoverdine siderophore biosynthesis in Pseudomonas aeruginosa PAO1.

The fluorescent dihydroxyquinoline chromophore of the pyoverdine siderophore in Pseudomonas is a condensation product of D-tyrosine and l-2,4-diaminobutyrate. Both pvdH and asd (encoding aspartate beta-semialdehyde dehydrogenase) knockout mutants of Pseudomonas aeruginosa PAO1 were unable to synthesize pyoverdine under iron-limiting conditions in the absence of l-2,4-diaminobutyrate in the culture media. The pvdH gene was subcloned, and the gene product was hyperexpressed and purified from P. aeruginosa PAO1. PvdH was found to catalyze an aminotransferase reaction, interconverting aspartate beta-semialdehyde and l-2,4-diaminobutyrate. Steady-state kinetic analysis with a novel coupled assay established that the enzyme adopts a ping-pong kinetic mechanism and has the highest specificity for alpha-ketoglutarate. The specificity of the enzyme toward the smaller keto acid pyruvate is 41-fold lower. The enzyme has negligible activity toward other keto acids tested. Homologues of PvdH were present in the genomes of other Pseudomonas spp. These homologues were found in the DNA loci of the corresponding genomes that contain other pyoverdine synthesis genes. This suggests that there is a general mechanism of l-2,4-diaminobutyrate synthesis in Pseudomonas strains that produce the pyoverdine siderophore.

Aminobutyrates↗
PubMedDate not supplied

[Application of carboxyline in prophylaxis of subclinical ketoses in lactating cows].

The feeding of carboxyline to lactating cows, their maintenance in rations balanced for the sugar-protein proportion and organization of the active exercises favour normalization of metabolism with subclinical ketoses. This is accompanied by a decrease in the content of ketonic bodies in blood, milk and urine with a simultaneous increase in the amount of citric acid. The content of sugar and alkaline reserves in blood increases, the amount of pyruvic acid decreases.

Acidosis↗
PubMed1978

Metabolism and the triggering of germination of Bacillus megaterium. Concentrations of amino acids, organic acids, adenine nucleotides and nicotinamide nucleotides during germination.

A considerable amount of evidence suggests that metabolism of germinants or metabolism stimulated by them is involved in triggering bacterial-spore germination. On the assumption that such a metabolic trigger might lead to relatively small biochemical changes in the first few minutes of germination, sensitive analytical techniques were used to detect any changes in spore components during the L-alanine-triggered germination of Bacillus megaterium KM spores. These experiments showed that no changes in spore free amino acids or ATP occurred until 2-3 min after L-alanine addition. Spores contained almost no oxo acids (pyruvate, alpha-oxoglutarate, oxaloacetate), malate or reduced NAD. These compounds were again not detectable until 2-3 min after addition of germinants. It is suggested, therefore, that metabolism associated with these intermediates is not involved in the triggering of germination of this organism.

Adenine Nucleotides↗
PubMed1975

Erythritol catabolism by Brucella abortus.

Cell extracts of Brucella abortus (British 19) catabolized erythritol through a series of phosphorylated intermediates to dihydroxyacetonephosphate and CO-2. Cell extracts required adenosine 5'-triphosphate (ATP), nicotinamide adenine dinucleotide (NAD), Mg2+, inorganic orthophosphate, and reduced glutathione for activity. The first reaction in the pathway was the phosphorylation of mesoerythritol with an ATP-dependent kinase which formed d-erythritol 1-phosphate (d-erythro-tetritol 1-phosphate). d-Erythritol 1-phosphate was oxidized by an NAD-dependent dehydrogenase to d-erythrulose 1-phosphate (d-glycero-2-tetrulose 1-phosphate). B. abortus (US-19) was found to lack the succeeding enzyme in the pathway and was used to prepare substrate amounts of d-erythrulose 1-phosphate. d-Erythritol 1-phosphate dehydrogenase (d-erythro-tetritol 1-phosphage: NAD 2-oxidoreductase) is probably membrane bound. d-Erythrulose 1-phosphate was oxidized by an NAD-dependent dehydrogenase to 3-keto-l-erythrose 4-phosphate (l-glycero-3-tetrosulose 4-phosphate) which was further oxidized at C-1 by a membrane-bound dehydrogenase coupled to the electron transport system. Either oxygen or nitrate had to be present as a terminal electron acceptor for the oxidation of 3-keto-l-erythrose 4-phosphate to 3-keto-l-erythronate 4-phosphate (l-glycero-3-tetrulosonic acid 4-phosphate). The beta-keto acid was decarboxylated by a soluble decarboxylase to dihydroxyacetonephosphate and CO-2. Dihydroxyacetonephosphate was converted to pyruvic acid by the final enzymes of glycolysis. The apparent dependence on the electron transport system of erythritol catabolism appears to be unique in Brucella and may play an important role in coupling metabolism to active transport and generation of ATP.

Adenosine Triphosphate↗
PubMed2005

Cell cycle synchronization of Cupriavidus necator by continuous phasing measured via flow cytometry.

The continuous phasing technique was successfully used to obtain a high degree of cell cycle synchrony in cultures of the model organism Ralstonia eutropha JMP 134 (today reclassified into Cupriavidus necator). The responses of the organism were evaluated with flow cytometric determinations of DNA contents and cell size (by fluorescence and forward scatter measurements, respectively, after staining with the DNA-binding dye 4',6-diamidino-2'-phenylindole, DAPI), and cell concentration, after staining with the nucleic acid binding dye LDS-751. The strain was cultivated on a mineral medium with pyruvic acid sodium salt as the limiting carbon and energy source. Famine conditions, and thus cell dormancy, were achieved in every cycle. The best synchronization, according to the determination of DNA contents, was induced with phasing cycle durations of at least 4 h. The method allows the induction of synchrony for an indefinite period if the medium is exchanged rapidly and precisely. The results show that the time required for a complete cell cycle of Cupriavidus necator JMP 134 is independent of the chosen phasing cycle duration, provided that each process cycle lasts at least 3 h which is much longer than the time needed for a single DNA replication cycle. With shorter cycling periods DNA-synthesis is carried out in an uncoupled manner and only weak cell cycle synchrony can be attained. The results also show that DNA-synthesis can only be undertaken by cells when they have exceeded a critical size.

Bioreactors↗
PubMed1977

Keto acids and free amino acids during leaf growth in Bauhinia purpurea L.

The biosynthesis of keto acids and free amino acids was studied during the growth of Bauhinia purpurea leaves. Alpha-KGA, OAA, pyruvic acid and PEP are the important keto acids observed at various stages. The first 2 metabolites show a progressive increase and PEP leads to OAA pathway is very active during the process of growth.

Amino Acids↗
PubMed2005

Overexpression of a hydrogenase gene in Clostridium paraputrificum to enhance hydrogen gas production.

A [Fe]-hydrogenase gene (hydA) was cloned from Clostridium paraputrificum M-21 in Escherichia coli using a conserved DNA sequence of clostridial hydrogenase genes amplified by PCR as the probe. The hydA gene consisted of an open reading frame of 1749 bp encoding 582 amino acids with an estimated molecular mass of 64,560 Da. It was ligated into a shuttle vector, pJIR751, originally constructed for Clostridium perfringens and E. coli, and expressed in C. paraputrificum. Hydrogen gas productivity of the recombinant increased up to 1.7-fold compared with the wild-type. In the recombinant, overexpression of hydA abolished lactic acid production and increased acetic acid production by over-oxidation of NADH, which is required for reduction of pyruvic acid to lactic acid in the wild-type.

Amino Acid Sequence↗