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PubMed1983

Nitrogenase activity (acetylene reduction) of root-associated, cold-climate azospirillum, enterobacter, Klebsiella, and pseudomonas species during growth on various carbon sources and at various partial pressures of oxygen.

A comprehensive view of the diazotrophic bacterial flora of plants requires that attention be paid to the appropriate carbon and oxygen requirements during isolation of the bacteria. Twenty compounds (monosaccharides, disaccharides, polyols, and organic acids) were therefore examined as carbon and energy sources for nitrogenase activity in semisolid stab cultures at pO(2) values of 0.21, 0.02, and </=0.002 with 12 strains of diazotrophic root-associated bacteria. With the facultatively anaerobic bacteria of the genera Klebsiella and Enterobacter, the best substrate was sucrose, followed by fructose and mannitol, whereas among the organic acids, only malic and fumaric acids supported any activity. With the obligately aerobic bacteria of the genera Azospirillum and Pseudomonas, disaccharides were not utilized for nitrogen fixation, but several organic acids were accepted in addition to monosaccharides and polyols; malate and glucose were the best substrates. The patterns of the carbon sources utilized for nitrogen fixation were coherent within the species, with the exception of one Klebsiella pneumoniae and one Enterobacter agglomerans strain, both isolated from the same individual grass plant, which were unable to utilize lactose. Anaerobic conditions (pO(2) value of </=0.002) were required for maximum nitrogenase activity with the facultatively anaerobic bacteria, with the exception of one strain of E. agglomerans, which required atmospheric oxygen (pO(2) value of 0.21). Also, the obligately aerobic diazotrophs required atmospheric oxygen for maximum nitrogenase activity. The maximum specific nitrogenase activities (expressed as micromoles of C(2)H(4) . milligram of bacterial protein . hour) noted during the exponential growth phase of the bacteria were the following: 2.68 with Azospirillum lipoferum on malate, 2.41 with K. pneumoniae and 1.58 with E. agglomerans on sucrose, and 0.95 with Pseudomonas sp. on malate.

Journal Article↗
PubMed2003

Growth inhibition of a phytopathogenic fungus, Colletotrichum species by acetic acid.

Acetic, oxalic, malic, and citric acids significantly inhibited the growth of Colletotrichurm, gloeosporioides, a phytopathogenic fungus, and acetic acid showed the strongest inhibition with no growth at 50 mM. The growth inhibition by these organic acids was closely related with the inhibition of respiration, as tested using three species, C. gloeosporioides, C. coccodes, and C. dermatium. Optimum growth of C. gloeosporioides was observed around pH 6.0. The inhibition of growth by acetic acid accelerated along with a decrease in pH from 6.0 to 4.0, suggesting that the inhibition might be more enhanced by undissociated form of acetic acid. Despite of growth inhibition by acetic acid, the fungus was able to grow in a normal medium when acetic acid was eliminated, implying that the growth inhibition may be resulted from an acetic acid-mediated inhibition of respiration than a structural damage of cell. Catalase activity of the fungus increased in response to 0.1% hydrogen peroxide, but addition of this together with 30 mM acetic acid brought about a decrease in the activity. The fungus which showed no grow at 30 mM acetic acid or 0.5% hydrogen peroxide began to grow after the elimination of these. But the fungus added simultaneously by these two compounds did not grow at all despite the elimination of these. Thus, controlling of Colletotrichum might be developed using acetic acid which is generally less dangerous than chemical reagents.

Acetic Acid↗
PubMed2002

Effect of organic acids on adsorption and desorption of rare earth elements.

Effect of citric, malic, tartaric and acetic acids on adsorption of La, Ce, Pr and Nd by and desorption from four typical Chinese soils was studied. Generally, adsorption capacities of rare earth elements (REEs) were significantly correlated with the cation exchange capacity (CEC) of soils. In the presence of acetic acids adsorption of REEs was similar to that in the presence of Ca(NO3)2. However, in the presence of citric, malic and tartaric acids adsorption of REEs by Heilongjiang, Zhejiang and Guangdong soils decreased to varying extents if compared with that in the presence of nitrate and acetic acid. The significance of suppression followed the order of citric acid > malic acid > tartaric acid > acetic acid, which was consistent with the order of stability of complexes of REEs with these organic acids. However, the adsorption increased with increasing equilibrium solution pH. For Jiangxi soil with low soil pH, CEC and organic matter these organic acids exerted an even more serious suppression effect on the adsorption of REEs. Another feature of the relationship between the adsorption of REEs and equilibrium solution pH was that the adsorption of REEs decreased with increase of pH from 2 to 4.5 and then slightly increased with further increase of pH. Desorption of REEs varied with soils and with organic acids as well. REEs were released easily from Heilongjiang, Zhejiang and Guangdong soils in the presence of organic acid. Generally, desorption of REEs decreased with increasing equilibrium solution pH. Effect of organic acids on desorption of REEs from Jiangxi soil was more complicated. In the presence of citric and malic acids no decrement and/or slight increase in desorption of REEs were observed over the equilibrium solution pH from 3 to 6.5. The reasons for this were ascribed to the strong complexing capacity of citric and malic acids and low soil pH, CEC and organic matter of Jiangxi soil.

Acetic Acid↗
PubMed1984

Malic enzyme and fatty acid synthase in the uropygial gland and liver of embryonic and neonatal ducklings. Tissue-specific regulation of gene expression.

Malic enzyme [L-malate-NADP oxidoreductase (decarboxylating), EC 1.1.1.40] and fatty acid synthase activities were barely detectable in the uropygial gland of duck embryos until 4 or 5 days before hatching, when they began to increase. These activities increased about 30- and 140-fold, respectively, by the day of hatching. Malic enzyme and fatty acid synthase activities were also very low in embryonic liver. However, hepatic malic enzyme activity did not increase until the newly hatched ducklings were fed. Hepatic fatty acid synthase began to increase the day before hatching and the rate of increase in enzyme activity accelerated markedly when the newly hatched ducklings were fed. Starvation of newly hatched or 12-day-old ducklings had no effect on the activities of malic enzyme and fatty acid synthase in the uropygial gland but markedly inhibited these activities in liver. Changes in the concentrations of both enzymes and in the relative synthesis rates of fatty acid synthase correlated with enzyme activities in both uropygial gland and liver. Developmental patterns for sequence abundance of malic enzyme and fatty acid synthase mRNAs in uropygial gland and liver were similar to those for their respective enzyme activities. Starvation of 4-day-old ducklings had no significant effect on the abundance of these mRNAs in uropygial gland but caused a pronounced decrease in their abundance in liver. It is concluded that developmental and nutritional regulation of these enzymes is tissue specific and occurs primarily at a pretranslational level in both uropygial gland and liver.

Animals↗
PubMed1992

Hexanoate and octanoate inhibit transcription of the malic enzyme and fatty acid synthase genes in chick embryo hepatocytes in culture.

Hexanoate and octanoate inhibit the triiodothyronine (T3)-induced increases in the activities of malic enzyme and fatty acid synthase in chick embryo hepatocytes in culture. Butanoate was less effective as an inhibitor, and palmitate, stearate, and oleate had no effect or small stimulatory effects. Hexanoate and octanoate inhibited the lipogenic enzyme activities at a transcriptional step, and did so within 30 min of addition. Incubation for 2 h in the absence of fatty acid reversed the inhibition of transcription caused by hexanoate. The inhibitory effect of hexanoate was selective because DNA content and transcription of the glyceraldehyde-3-phosphate dehydrogenase and beta-actin genes were not inhibited. Hexanoate-mediated inhibition of transcription rates of the lipogenic genes was not correlated with an inhibition of binding of T3 to its nuclear receptor. 2-Bromooctanoate and carnitine stimulated the T3-induced accumulation of the mRNAs for malic enzyme and fatty acid synthase. The presence of hexanoate stimulated by 2- to 3-fold the increase caused by carnitine, suggesting that hexanoate and carnitine may regulate lipogenic gene expression by a common pathway. Hexanedioate, acetoacetate, beta-hydroxybutyrate, branched chain fatty acids, and branched chain keto acids had little or no effect on abundance of the lipogenic mRNAs. We suggest that the active inhibitor is a metabolite derived from hexanoate or octanoate, possibly an intermediate derived from an acyl-CoA derivative.

Actins↗
PubMed2005

Stimulation of Erwinia sp. fumarase and aspartase synthesis by changing medium components.

The optimal concentrations of nutrient medium components, aeration conditions, and pH providing for maximum biomass yields, as well as fumarase and L-aspartase activities, during submerged cultivation of Erwinia sp. were determined. The data showed that different concentrations of carbon source (molasses) and pH of the nutrient medium were required to reach the maximum fumarase and L-aspartase activities. Calculations performed by application of the additive lattice model suggested that the combination of these optimized factors would result in 3.2-, 3.4-, and 3.8-fold increases as compared to the experimental means in Erwinia sp. biomass, and L-aspartase and fumarase activities, respectively. The conditions of the fumaric acid biotransformations into L-malic and L-aspartic acids were optimized on the basis of intact Erwinia sp. cells, a fumarase and L-aspartase producer. In the cases of fumarate transformation into L-malic acid and of fumarate transformation into L-aspartic acids, fumarase and L-aspartase activities increased 1.5- and 1.7-fold, respectively. The experimental data were consistent with these estimates to 80% accuracy. In comparison with the additive lattice model, the application of polynomial nonlinear model allowed the between-factor relations to be considered and analyzed, which resulted in 1.1-, 1.27-, and 1.1-fold increases in Erwinia sp. biomass and fumarase and L-aspartase activities for the case of cultivation. In the case of fumarate transformation into L-malic acid, this model demonstrated a 1.7-fold increase in fumarase activity, whereas during fumarate transformation into L-aspartic acid no significant change in aspartase activity was observed.

Algorithms↗
PubMed2004

High-performance liquid chromatographic separation and quantification of citric, lactic, malic, oxalic and tartaric acids using a post-column photochemical reaction and chemiluminescence detection.

An HPLC method was developed for the determination of citric, lactic, malic, oxalic and tartaric acids by chemiluminescent detection following online irradiation with visible light. The organic acids were irradiated with visible light in the presence of Fe3+ and UO2(2+) to generate Fe2+, which was determined by measuring the chemiluminescence intensity in a luminol system in the absence of added oxidant. Factors affecting the photochemical and chemiluminescence reactions were optimised so that their contribution to the total band-broadening was negligible. The chromatographic separation was performed on a C18 column under isocratic reversed-phase conditions using 0.005 M H2SO4 mobile phase. The optimised method was validated with respect to linearity, precision, limits of detection and quantification, accuracy specificity and robustness. The applicability of the assay was demonstrated by analysing these compounds in real samples such as milk, fruit juices, soft drinks, wine and beer.

Acids↗
PubMed1980

Synergism of thyroid hormone and high carbohydrate diet in the induction of lipogenic enzymes in the rat. Mechanisms and implications.

We have investigated the relationship between the administration of triiodothyronine (T3) and a high carbohydrate (CHO) fat-free diet in the induction of lipogenic enzymes in two rat tissues, liver, and fat. Male thyroidectomized rats were treated with graded daily doses of T3 and either supplemented with a high CHO diet or left on a regular diet. Enzymes studied included malic enzyme (ME), fatty acid synthetase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase. In the liver, all four lipogenic enzymes showed a synergistic response between T3 administration and high CHO feeding. In fat, ME also responded synergistically. The interaction was reflected in an increased sensitivity to T3. The dose of T3 required to achieve 50% maximal response was reduced three- to seven-fold by the high CHO diet. This phenomenon could not be attributed to a dietary-induced alteration either in T3 metabolism or in number or affinity of the T3-nuclear receptors. Moreover, studies of the relative rate of synthesis of ME suggested a simultaneous time of onset in the induction of ME, within 2 h after the application of either T3 or CHO. Thus, it is unlikely that either stimulus is secondary to the other. Since parallel experiments from this laboratory (Towle, Mariash, and Oppenheimer,1980. Changes in hepatic levels of messenger ribonucleic acid for malic enzyme during induction by thyroid hormone or diet. Biochemistry. 19: 579-585.) show that ME induction both by CHO and T3 is mediated by an increase in specific messenger RNA for ME, the interaction of T3 and the dietary factor occurs at a pretanslational level.

Adipose Tissue↗
PubMed1996

Mode of action of the yeast Saccharomyces cerevisiae as a feed additive for ruminants.

Two suggested modes of action of yeast in stimulating rumen fermentation were investigated. The first, that yeast respiratory activity protects anaerobic rumen bacteria from damage by O2, was tested using different strains of yeast that had previously been shown to have differing abilities to increase the viable count of rumen bacteria. Saccharomyces cerevisiae NCYC 240, NCYC 1026, and the commercial product Yea-Sacc, added to rumen fluid in vitro at 1.3 mg/ml, increased the rate of O2 disappearance by between 46 and 89%. The same three preparations also stimulated bacterial numbers in an in vitro fermenter (Rusitec). S. cerevisiae NCYC 694 and NCYC 1088, which had no influence on the viable count in Rusitec, also had no effect on O2 uptake. Respiration-deficient (RD) mutants of S. cerevisiae NCYC 240 and NCYC 1026 were enriched by repeated culturing in the presence of ethidium bromide. S. cerevisiae NCYC 240 and NCYC 1026 stimulated the total and cellulolytic bacterial populations in Rusitec, while the corresponding RD mutants did not. Rigorous precautions to exclude air from Rusitec resulted in S. cerevisiae NCYC 240 no longer stimulating total bacterial numbers, although it still increased numbers of cellulolytic bacteria. The second hypothesis, that yeast provides malic and other dicarboxylic acids which stimulate the growth of some rumen bacteria, was examined by comparing the effects of yeast and malic acid on rumen fermentation in sheep. Three mature sheep were given 0.85 kg barley/d plus 0.55 kg chopped ryegrass hay/d either unsupplemented, or supplemented with 4 g S. cerevisiae NCYC 240/d or 100 mg L-malic acid/d either mixed with the diet or in aqueous solution infused continuously into the rumen. Yeast increased the total viable count of bacteria (P < 0.05) whereas malic acid did not, and no other effect of the treatments reached statistical significance. It was concluded, therefore, that the stimulation of rumen bacteria by S. cerevisiae is at least partly dependent on its respiratory activity, and is not mediated by malic acid.

Animals↗
PubMed1968

Fixation of carbon dioxide in the dark by the malic enzyme of bean and oat stem rust uredospores.

Malic enzyme was found in both bean rust and cat stem rust uredospores. In bean rust uredospores it was shown to catalyze the formation of pyruvic acid from l-malic acid and to synthesize malic acid from pyruvic acid and CO(2). The malic enzyme from bean rust uredospores was specific for NADP and dependent on manganous ions for activity. The specific activity of the bean rust malic enzyme in crude extracts of ungerminated uredospores was approximately 6 times greater than that found in crude extracts obtained from germinated uredospores. The malic enzyme was also found in extracts obtained from healthy and rust-infected bean leaves. The specific activity of the enzyme was approximately 2 to 5 times greater in partially purified extracts obtained from the infected bean tissue at 6 days after inoculation. The specific activity of the malic enzyme in crude extracts obtained from oat stem rust uredospores was 2 times greater than the specific activity of this enzyme in crude extracts obtained from bean rust uredospores. Phosphoenolpyruvate carboxylase activity could not be demonstrated in crude extracts obtained from the ungerminated uredospores of the bean rust fungus.

Journal Article↗
PubMed1999

Association of fatty acid synthase gene and malic enzyme gene polymorphisms with fatness in turkeys.

A candidate gene approach was carried out on a commercial line of turkeys to assess the association between fatness variability and polymorphisms of genes involved in lipid metabolism. Four restriction fragment length polymorphisms (RFLP) were typed on the fatty acid synthase gene (MspI/pF5), on the malic enzyme gene (HindIII/em), as well as on the acetyl coenzyme A carboxylase and delta9 desaturase genes. Fatness level was estimated in vivo by an ultrasonic instrument. Fat yield was assessed after slaughter by calculating the ratio of the leg skin plus subcutaneous fat weight to the whole leg weight. Finally, the lipid content was determined by extraction from the boneless leg. The 84 female turkeys sampled were full and half-sibs born from eight sires, seven of which were heterozygous for MspI/pF5 or HindIII/em RFLP and one of which was double homozygous at these loci. The analyses of variance used to compare the genotypes at each RFLP suggested a major role associated with the fatty acid synthase gene polymorphism in the explanation of fatness variability. One homozygous genotype for MspI/pF5 was about 1.5 standard deviations leaner than the other two homozygous genotypes. An analysis of the average effects of gene substitution confirmed the association between leanness and one allele of the fatty acid synthase polymorphism. It also identified a significant association between leanness and one malic enzyme RFLP allele, congruent with a strictly additive determinism for the effect associated with this polymorphism. This experiment provided new evidence of the association between both fatty acid synthase and malic enzyme gene polymorphisms and fatness variability in turkeys.

Animals↗
PubMed1980

Relationship of malic enzyme activity to fatty acid synthesis and the pathways of glucose catabolism in developing rat liver.

The rates of fatty acid synthesis and the activity of several enzymes involved in lipid and carbohydrate metabolism were determined in livers from fetal, suckling, weanling and maternal rats. An estimate of the proportion of glucose catabolized via the pentose phosphate cycle and the Embden-Meyerhoff pathway was made using 14C- and 3H-labeled glucose. The contribution of pentose phosphate cycle-generated reducing equivalents to fatty acid synthesis was assessed using glucose-3-3H. Developmental changes in the activity of hepatic malic enzyme were not related to developmental changes in the rate of fatty acid synthesis as might be expected if this enzyme functioned to provide NADPH for fatty acid synthesis. Malic enzyme activity did not correlate with pentose phosphate cycle activity or with utilization for fatty acid synthesis of NADPH generated via this pathway.

Acetates↗
PubMed1986

Regulation of hepatic malic enzyme by perfluorodecanoic acid.

Perfluorodecanoic acid (PFDA) administration to adult male rats increased both the activity of hepatic malic enzyme and liver weight in a dose-dependent manner. Hepatomegaly and augmented activity of malic enzyme in liver were apparent within one day following PFDA administration and reached a plateau by three days posttreatment. Malic enzyme quantity per liver in PFDA-treated rats was elevated within one day following dosing and increased continually throughout five days posttreatment. Administration of PFDA to rats in the fed state also led to an increase in the specific activity of hepatic malic enzyme that peaked at three days following dosing. When compared to the fed condition, rats fasted for 48 hours had a decrease in both relative liver weight and the quantity of supernatant protein per liver. The total activity (U/liver) and specific activity of malic enzyme in the liver were also reduced in the fasted state. During the 24 hours after treatment in rats fasted for 48 hours, the body weight as well as the absolute and relative liver weight of animals receiving vehicle declined continuously in the absence of feed. Following the administration of PFDA to fasted rats, body weight was maintained until eight hours posttreatment but then declined at a rate similar to that found with the vehicle-treated group. Absolute and relative liver weight in PFDA-treated rats were increased significantly at eight hours posttreatment when compared to those receiving vehicle, and this increment was maintained throughout the rest of the 24 hours following dosing. While the activity and enzyme content of hepatic malic enzyme decreased in the vehicle-treated group, administration of PFDA to rats fasted for 48 hours prevented their decline. The specific activity of hepatic malic enzyme in 48 hours fasted rats receiving PFDA was also elevated significantly at 16 hours posttreatment. Thus, the administration of PFDA to the adult male rat in both the fed and fasted nutritional states was found to regulate hepatic malic enzyme by not only increasing enzyme quantity but also by augmenting the specific activity, (ie, catalytic state) of the enzyme.

Animals↗