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PubMed1979

Dark Carbon Dioxide Fixation under Aerobic and Anaerobic Conditions in Maize Leaves after Preillumination in the Absence of Oxygen: Ribulose 1,5-Bisphosphate Can Serve as a Primary Acceptor of Carbon Dioxide.

When dark (14)CO(2) fixation in maize leaves was carried out under anaerobic conditions after preillumination in the absence of O(2), the (14)C incorporation in aspartic acid was transient; its maximum level was very low compared with that of malic acid. The addition of 5% O(2) during the dark fixation period increased the total uptake of (14)CO(2) and the (14)C incorporation into aspartic acid.A study of the intramolecular distribution of radioactivity showed that 71 to 76% of the (14)C was located in the C(4) (beta-carboxyl) of malate and aspartate and the remainder in the C(1). This intramolecular labeling pattern did not change during the 5- to 60-second dark (14)CO(2) fixation period and was scarcely altered by the presence of O(2). Three degradation techniques led to similar data.The significance of these results is discussed taking into account the known possible carboxylation pathways. It is concluded that ribulose 1,5-bisphosphate can be a primary acceptor of CO(2) when maize leaves are preilluminated in the absence of O(2).

Journal Article↗

PubMed1992

Metabolism of L-amino acids in a marine bacterium isolated from mackerel intestines in relation to eicosapentaenoic acid biosynthesis.

Metabolism of glucose and L-amino acids in an obligately aerobic marine bacterium isolated from Pacific mackerel intestines was investigated for the mechanism and pathway of eicosapentaenoic acid (EPA) biosynthesis. This bacterium could not uptake glucose but the cell-free extract of this bacterium had the enzymatic activities of L-alanine oxidase (EC 1.4.3.2), L-alanine dehydrogenase (EC 1.4.1.1). L-serine dehydratase (EC 4.2.1.13), and malate dehydrogenase (EC 1.1.1.40), and of seven enzymes involved in the TCA cycle of the usual aerobes. On the other hand, the carbon-13 concentration in cellular fatty acids of the bacterium, especially that in their methyl carbon atoms in contrast to their carbonyl carbons, increased drastically when the bacterium was grown in the presence of 13CH3COONa. These results indicate that: (i) the TCA cycle works in this bacterium, (ii) glucose is not utilized and pyruvic acid is in vivo synthesized from L-alanine, L-serine, and malic acid, and (iii) EPA and other cellular fatty acids are in vivo synthesized from acetyl coenzyme A by the usual de novo synthesis route.

Amino Acids↗

PubMed1977

1,1-Dichloroethylene hepatotoxicity: proposed mechanism of action and distribution and binding of 14C radioactivity following inhalation exposure in rats.

1,1-Dichloroethylene is reported to produce renal tumors in male mice. It is an hepatotoxin in fasted rats after inhalation. We found that trichloropropane epoxide, an inhibitor of epoxide hydrase, enhances hepatic injury as measured by serum sorbitol dehydrogenase elevation. A significant elevation of hepatic citric acid concentration was seen in fasted but not fed rats. We hypothesized that mitochondrial injury was associated with inhibition of the tricarboxylic acid cycle and postulated that monochloroacetic acid was a toxic metabolite of 1,1-DCE. Fluoroacetic acid and chloroacetic acid were similar in their ability to inhibit oxygen uptake when pyruvic and malic acids were substrates in isolated mitochondria supplemented with adenosine diphosphate. In experiments where 1,1-DCE metabolism was estimated, no difference between the rate of uptake in a 2-hr period was detected between fed and fasted animals. Urinary output of radioactivity at 26 hr for fed and fasted rats was similar. Water-soluble (i.e. TCA-soluble) 1,1-DCE metabolites were found in tissues of fasted rats in excess of that seen in fed rats. The kidney had the largest concentration of total metabolites. Tissue-bound, or TCA-insoluble, radioactivity was associated with the mitrochondrial and microsomal fraction of fasted rats in excess of that seen in fed rats. The disappearance of TCA-insoluble radioactivity from the mitochondrial and microsomal fractions was comparable in rate between fed and fasted rats respectively. These results suggest that 1,1-DCE is metabolized quite rapidly in the organism to TCA-soluble components which are excreted by the kidneys. Metabolites of 1,1-DCE may enter the metabolic pool, since a reasonably short turnover of (14)C-labeled, bound material was observed. The metabolite of 1,1-DCE appears to inhibit the mitochondria so that citric acid accumulates. This may occur by a process of lethal synthesis.

Acetates↗

PubMed1998

Glucose stimulates transcription of fatty acid synthase and malic enzyme in avian hepatocytes.

Transcription of fatty acid synthase (FAS) and malic enzyme (ME) in avian liver is low during starvation or feeding a low-carbohydrate, high-fat diet and high during feeding a high-carbohydrate, low-fat diet. The role of glucose in the nutritional control of FAS and ME was investigated by determining the effects of this metabolic fuel on expression of FAS and ME in primary cultures of chick embryo hepatocytes. In the presence of triiodothyronine, glucose (25 mM) stimulated an increase in the activity and mRNA abundance of FAS and ME. These effects required the phosphorylation of glucose to glucose 6-phosphate but not further metabolism downstream of the aldolase step of the glycolytic pathway. Xylitol mimicked the effects of glucose on FAS and ME expression, suggesting that an intermediate of the pentose phosphate pathway may be involved in mediating this response. The effects of glucose on the mRNA abundance of FAS and ME were accompanied by similar changes in transcription of FAS and ME. These data support the hypothesis that glucose plays a role in mediating the effects of nutritional manipulation on transcription of FAS and ME in liver.

Acyltransferases↗

PubMed1975

Absorption, distribution, and metabolic fate of 7-chloro-3,3a-dihydro-2-methyl-2H,9H-isoxazolo-(3,2-b)(1,3)-benzoxazin-9-one in rats, dogs, and humans.

The absorption and metabolic fate of 7-chloro-3,3a-dihydro-2-methyl-2H,9H-isoxazolo-(3,2-b)(1,3)-benzoxazin-9-one (I) was studied in rats, dogs, and humans. Orally administered I was readily absorbed by all species. In the rat, orally administered I was converted to its metabolite, 5-chlorosalicylic acid, by the intestinal wall. The half-lives of blood radioactivity, after the oral administration of I-9-14C, were about 18 and 12 hr in the rat and beagle hound, respectively. In human subjects, no intact I was detected in the bloodstream; however, the clearance of the metabolite, 5-chlorosalicylic acid, had a half-life of about 33 hr. Cleavage of the oxazine ring of I generated 5-chlorosalicylic acid, which was excreted both in the free form and conjugated with glycine and glucuronic acid. The isoxazole moiety was converted to beta-hydroxybutyric acid and its metabolites carbon dioxide and fumaric, citric, alpha-ketoglutaric, succinic, and malic acids. Binding of I to plasma proteins was extensive but was less than that of 5-chlorosalicylic acid.

Animals↗

PubMed2002

Aspartame optical biosensor with bienzyme-immobilized eggshell membrane and oxygen-sensitive optode membrane.

An aspartame optical biosensor has been fabricated by employing a bienzyme system composed of alpha-chymotrypsin and alcohol oxidase immobilized onto an eggshell membrane and an oxygen-sensitive optode membrane as the transducer. The detection schemes involve the enzymatic reactions of aspartame leading to the depletion of the oxygen level of the medium with a concomitant enhancement of the fluorescence intensity of the oxygen-sensitive membrane. The scanning electron and transmission electron micrographs show the microstructure of the eggshell membrane which is successfully immobilized with bienzyme. Using this novel immobilization technique, the aspartame biosensor shows extremely good stability with a shelf life of at least 8 months. The rate change of the fluorescence intensity in 4 min is found to be linearly related to the concentration of aspartame. The useful analytical working range of the biosensor is from 0.056 to 3.07 mM aspartame. The effects of temperature, pH, and ionic strength on the response of the aspartame biosensor are investigated in detail. Citric acid, cyclamic acid, D-fructose, D-galactose, D-glucose, hydrogen peroxide, DL-malic acid, L-phenylalanine, saccharin, sodium benzoate, and sucrose show no interferences but ethanol interferes strongly. The aspartame biosensor has been applied to determine aspartame contents in some commercial products.

Animals↗

PubMed1988

Citric, malic and succinic acids as possible alternatives to deferoxamine in aluminum toxicity.

The effect of repeated intraperitoneal administration of deferoxamine, citric, malic and succinic acids on the distribution and excretion of aluminum was determined in male Swiss mice which had previously received aluminum nitrate intraperitoneally at a daily dose of 0.27 mmol/kg for five weeks. Chelating agents were administered for two weeks at doses approximately equal to one-fourth of their respective LD50. Treatment with DFOA, citric, malic or succinic acids significantly increased the fecal and urinary excretion of aluminum and reduced the concentration of aluminum found in various organs and tissues, with citric acid being the most effective. In sight of these results, citric, malic or succinic acids may be considered as alternatives to deferoxamine in aluminum toxicity. However, further investigations are required previous to the possible use of these compounds in human aluminum poisoning.

Aluminum↗

PubMed1979

Investigation of effect of alpha-naphthylamine and beta-naphthylamine on organic acids formation of self-sustaining coacervates.

Malonic and oleic acids were found in the typical mixtures. Samples containing alpha-naphthylamine gave oleic and malic acids which disintegrated with time of exposure. Tricarballylic acid was confirmed in presence of beta-naphthyl amine, but disappeared with time. Arachidic, tartaric, and adipic acids were found, but they disappeared in eight days' exposed samples. At later stages of exposure, malonic acid was observed along with sporadic appearances of citric , succinic, and oleic acids. Rate of disintegration of these compounds was directly proportional to time of exposure to sunlight.

1-Naphthylamine↗

PubMed1982

D-Malic enzyme of Pseudomonas fluorescens.

By the enrichment culture technique 14 gram-negative bacteria and two yeast strains were isolated that used D(+)-malic acid as sole carbon source. The bacteria were identified as Pseudomonas putida, Pseudomonas fluorescens, Pseudomonas aeruginosa and Klebsiella aerogenes. In cell-free extracts of P. fluorescens and P. putida the presence of malate dehydrogenase, D-malic enzyme (NAD-dependent) and L-malic enzyme (NADP-dependent) was demonstrated. D-Malic enzyme from P. fluorescens was purified. Stabilization of the enzyme by 50 mM ammonium sulphate an 1 mM EDTA was essential. Preparation of D-malic enzyme that gave one band with disc gel electrophoresis showed a specific activity of 4-5 U/mg. D-Malic enzyme requires divalent cations. The Km values were for malate Km = 0.3 mM and for NAD Km = 0.08 mM. The pH optimum for the reaction was found to be in the range of pH 8.1 to pH 8.8. D-Malic enzyme is partially inhibited by oxaloacetic acid, meso-tartaric acid, D-lactic acid and ATP. Determined by gel filtration and gradient gel electrophoresis, the molecular weight was approximately 175 000.

Cell-Free System↗

PubMed2006

Changes in volatile compounds and related biochemical profile during controlled fermentation of cv. Conservolea green olives.

The effect of controlled fermentation processes on the profile of volatile and other biochemical compounds of cv. Conservolea green olives processed by the Spanish method was studied. The different treatments included: (a) inoculation with a commercial starter culture of Lactobacillus pentosus, (b) inoculation with a wild strain of Lactobacillus plantarum isolated from a previous fermentation, (c) uninoculated spontaneous process (control). Microbial growth, pH, titratable acidity, reducing sugars, organic acids and volatile compounds were monitored. Starter cultures were effective in establishing an accelerated fermentation process. Both were able to reduce the survival period of Enterobacteria by 7 days, minimizing thus the likelihood of spoilage. Higher acidification of the brines and faster pH drop was observed in inoculated processes, with L. pentosus presenting better performance than the wild strain of L. plantarum. Lactic and acetic were the major organic acids detected by HPLC, the concentration of which increased in the course of fermentation. Citric and malic acids were also present in the brines but they were degraded completely within the first 2 weeks of fermentation. Ethanol, methanol, acetaldehyde, ethyl acetate, isobutyric acid were the major volatile compounds identified by GC. Their concentration varied greatly among the fermentation processes, reflecting varying degrees of microbial activity in the brines.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

[Effect of exogenous acetyl group acceptors on cholinesterase biosynthesis in Arthrobacter simplex cells].

The presence of active acetyl or butyryl groups and their acceptors in the growth medium was found to be necessary for the high rate of cholinesterase biosynthesis in the cells of Arthrobacter simplex var. cholinesterasus. The active acetyl and butyryl groups are formed upon hydrolysis of acetylcholine and butyrylcholine as well as in the course of glucose metabolism. The following acids were shown to be the acceptors of the acetyl and butyryl groups: butyric, succinic, fumaric, malic acids and, to a less extent, alpha-ketoglutaric acid. The active acetyl and butyryl groups are bound with the acceptors under the control of coenzyme A in the reactions of fatty acid synthesis and the tricarboxylic acid cycle. Presumably, CoA regulates cholinesterase synthesis. The high rate of CoA binding in metabolic reactions provides conditions for the intensive synthesis of cholinesterase; the deceleration of these reactions inhibits the biosynthesis of cholinesterase.

Acetylation↗

PubMed2001

Importance of redox balance on the production of succinic acid by metabolically engineered Escherichia coli.

We had previously shown that succinic acid production in a pfl ldhA double mutant strain of Escherichia coli could be enhanced by amplifying the malic enzyme activity. However, recombinant E. coli NZN111 (F- Apfl::Cam ldhA::Kan) harboring pTrcML, a plasmid containing the E. coli malic enzyme gene, produced a considerable amount of malic acid along with the desired product, succinic acid. To have an insight into the intracellular metabolism, metabolic control analysis was carried out. From the results of a simulation, it was predicted that supplying additional reducing power could enhance succinic acid production. More reduced carbon substrate sorbitol was thus examined for the possibility of matching the potential during succinic acid production. When NZN111 (pTrcML) was cultured in LB medium containing 20 g sorbitol/l under a CO2 atmosphere, 10 g succinic acid/l was produced. The apparent yield of succinic acid was 1.1 g succinic acid/g sorbitol, which is 85% of the maximum theoretical yield. Therefore, it was found that redox balancing was important for the enhanced production of succinic acid in metabolically engineered E. coli.

Carbon Dioxide↗

PubMed1966

Compartmentation of organic acids in corn roots I. Differential labeling of 2 malate pools.

Bicarbonate-(14)C and acetate-(3)H were simultaneously provided to corn roots to give 2 isotopic forms of malate in the tissue, malate-(14)C produced by dark fixation reactions and malate-(3)H produced by reactions of the tricarboxylic acid cycle. Following a short pulse of exposure to the isotopes, the dissimilation of both isotopic forms of malic acid was followed. The rate of utilization of malate-(3)H was much faster than that of malate-(14)C.These results are interpreted as showing that the malate produced from (14)CO(2) is in a pool physically separated from that in the tricarboxylic acid cycle. The introduction of the 2 isotopes through distinct metabolic pathways produced the differential labeling of 2 distinct pools of malate.

Journal Article↗

PubMed1995

The mae1 gene of Schizosaccharomyces pombe encodes a permease for malate and other C4 dicarboxylic acids.

The mae1 gene of the yeast Schizosaccharomyces pombe was identified on the basis of its ability to complement a mutant defective in the transport of malic acid. Analysis of the DNA sequence revealed an open reading frame of 1314 base pairs, encoding a polypeptide of 438 amino acids with a predicted molecular weight of 49 kDa. A hydropathy profile of the predicted amino acid sequence revealed a protein with ten membrane-spanning or associated domains and hydrophilic N- and C- termini. The predicted secondary structure of the protein in similar to models proposed for other integral membrane proteins from both prokaryotes and eukaryotes. The S. pombe mae1 gene encodes a single mRNA of 1.5 kb. The mea1 gene is expressed constitutively and is not subject to catabolite repression as was previously reported for the malate permease systems of Candida utilis and Hansenula anomala. The mae1 gene was mapped 2842 bp 5' to the MFml gene on chromosome I. Transport assays revealed that the mae1 gene encodes a permease involved in the uptake of L-malate, succinate and malonic acid.

Amino Acid Sequence↗

PubMed1983

Effect of Varying CO(2) Partial Pressure on Photosynthesis and on Carbon Isotope Composition of Carbon-4 of Malate from the Crassulacean Acid Metabolism Plant Kalanchoë daigremontiana Hamet et Perr.

Intact leaves of Kalanchoë daigremontiana were exposed to CO(2) partial pressures of 100, 300, and 1000 microbars. Malic acid was extracted, purified, and degraded in order to obtain isotopic composition of carbon-1 and carbon-4. From these data, it is possible to calculate the carbon isotope composition of newly fixed carbon in malate. In all three treatments, the isotopic composition of newly introduced carbon is the same as that of the CO(2) source and is independent of CO(2) partial pressures over the range tested. Comparison with numerical models described previously (O'Leary 1981 Phytochemistry 20: 553-567) indicates that we would expect carbon 4 of malate to be 4 per thousand more negative than source CO(2) if diffusion is totally limiting or 7 per thousand more positive than source CO(2) if carboxylation is totally limiting. Our results demonstrate that stomatal aperture adjusts to changing CO(2) partial pressures and maintains the ratio of diffusion resistance to carboxylation resistance approximately constant. In this study, carboxylation and diffusion resistances balance so that essentially no fractionation occurs during malate synthesis. Gas exchange studies of the same leaves from which malate was extracted show that the extent of malate synthesis over the whole night is nearly independent of CO(2) partial pressure, although there are small variations in CO(2) uptake rate. Both the gas exchange and the isotope studies indicate that the ratio of external to internal CO(2) partial pressure is the same in all three treatments. Inasmuch as a constant ratio will result in constant isotope fractionation, this observation may explain why plants in general have fairly invariable (13)C contents, despite growing under a variety of environmental conditions.

Journal Article↗

PubMed2006

Effects of pH, organic acids, and inorganic ions on lead desorption from soils.

The desorption characteristics of lead in two variable charge soils (one developed from Arenaceous rock (RAR) and the other derived from Quaternary red earths (REQ)) were studied, and the effects of pH value, organic acid, and competitive ions were examined. Desorption of Pb(2+) decreased from nearly 100.0 to 20.0% within pH 1.0-4.0 in both soils, and then the decrease diminished at pH > 4.0. Organic ligands at relatively low concentrations (< or =10(-3) mol L(-1)) slightly inhibited Pb(2+) desorption, but enhanced Pb(2+) desorption at higher concentrations. In this study, citric acid or acetic acid at higher concentrations (>10(-3) mol L(-1)) had the greatest improvement of Pb(2+) desorption, followed by malic acid; and the smallest was oxalic acid. Desorption of the adsorbed Pb(2+) increased greatly with increasing concentrations of added Cu(2+) or Zn(2+). Applied Cu(2+) increased Pb(2+) desorption more than Zn(2+) at the same loading.

Acetic Acid↗

PubMed1959

Carbon dioxide fixation in marine invertebrates: a survey of major phyla.

Fourteen species of marine invertebrates representing 12 phyla were kept in sea water containing NaHC(14)O(2) for 1 hour. All of them fixed CO(2) into acids of the Krebs citric acid cycle. In most species the major portion of the radioactivity recovered after chromatography was in succinic, fumaric, and malic acids. The findings favor the hypothesis that both CO(2) fixation and the citric acid cycle are virtually universal among marine invertebrates.

Carbon Dioxide↗

PubMed1980

Urea-acetylene dicarboxylic acid reaction: a likely pathway for prebiotic uracil formation.

A number of routes have been suggested for the prebiotic synthesis of uracil involving the reaction of urea with malic acid, propiolic acid, cyanoacetylene and others. Cyanoacetylene has been detected in the interstellar medium as well as simulated prebiotic experiments. It is therefore plausible that dicyanoacetylene and its hydrolytic product acetylene dicarboxylic acid (ADCA) may have played a role in chemical evolution. This aspect has been examined in the present work for the synthesis of uracil from ADCA and urea reaction. It was found that when ADCA reacted with urea, uracil was formed only in the presence of phosphoric acid and phosphates. ammonium phosphates gave higher yields of uracil than other phosphates. In the absence of phosphoric acid or phosphates no uracil formation took place. This type of synthesis could have taken place in prebiotic oceans which contained ammonium phosphates and other salts.

Acetylene↗