Enzyme redundancy and the importance of 2-oxoglutarate in higher plant ammonium assimilation.
Explore the source record for details and available documents.
Aspartate Aminotransferases↗
SEARCH · PubMed Health
Results for “AMMONIA AND AMMONIUM COMPOUNDS”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Isolated brain microvessels as in vitro equivalents of the blood-brain barrier: selective removal by collagenase of the A-system of neutral amino acid transport.
On treatment with collagenase, brain microvessels, together with several protein components, lose some enzymatic activities such as alkaline phosphatase and gamma-glutamyltranspeptidase, whereas no change occurs in the activities of 5'-nucleotidase and glutamine synthetase. The energy-requiring "A-system" of polar neutral amino acid transport is also severely inactivated, whereas the L-system for the facilitated exchange of branched chain and aromatic amino acids is preserved. In the collagenase-digested microvessels, this leads to loss of the transtimulation effect of glutamine on the transport of large neutral amino acids, because such transtimulation is due to a cooperation between the A- and L-systems. By contrast, NH4+ maintains (and even enhances) its ability to stimulate the L-system of amino acid transport, presumably through glutamine synthesis within the endothelial cells.
5'-Nucleotidase↗
Novel mutant of Anabaena sp. strain CA which growns on N2 but not on combined nitrogen.
A mutant has been isolated from Anabaena sp. strain CA by treatment with N-methyl-N'-nitro-N-nitrosoguanidine, which has the unusual phenotypic characteristic of growth only under N2-fixing conditions. Growth of the mutant was completely inhibited by NO3- or NH4+ at concentrations routinely used for growth of the wild type, and sensitivity to NH4+ was especially pronounced. The inhibitory effect of NH4+ could not be overcome by glutamine, glutamate, or casein hydrolysate. Ammonia had no immediate inhibitory effect on protein synthesis, CO2 fixation, or O2 evolution, and the gradual inhibition of C2H2 reduction activity by NH4+ resembled a repression phenomenon. The glutamine synthetase activity of N2-fixing cultures appeared normal, yet the mutant was incapable of utilizing exogenous NH4+ for growth. Preliminary evidence suggests a possible alteration of glutamine synthetase, which could result in sensitivity to exogenous NH4+ by progressive inactivation of the enzyme or repression of its synthesis.
Amino Acids↗
Evidence for a glutamine synthetase-chromatophore association in the phototroph Rhodospirillum rubrum: purification, properties, and regulation of the enzyme.
The characteristics of soluble and membrane-bound glutamine synthetase (GS) from Rhodospirillum rubrum were compared with those of the enzyme located in situ (measured in detergent-treated cells). The results suggest that in vivo GS may be associated with, or bound to, the chromatophore membranes. GS was found to reversibly associate and dissociate from purified chromatophores as a function of the ionic strength of the buffer or the Mg2+ concentration. Solubilized GS was purified to homogeneity and found to be similar to the GS of enteric bacteria in that its molecular weight was about 600,000 and it had one type of subunit of 51,000 molecular weight. Removal of GS from the membrane had no effect on the Km values for the substrates of the biosynthetic reaction, but it did have a substantial effect on both its Mg2+ requirement (the Km increased 10-fold) and the sensitivity of the gamma-glutamyl transferase reaction to the inhibitor methionine sulfoximine (the I0.5 decreased from 1,500 to 60 microM). Both observations suggest that the active site of GS is influenced by its association with the membrane. GS activity was shown to respond to NH4+, phosphodiesterase, Mg2+, and adenylylation cofactors in a manner identical to that of the GS of the coliform bacteria, suggesting that the former may also respond to adenylylation and deadenylylation. Finally, R. rubrum GS was also inhibited by NH4+ by a newly observed, as yet undefined, system.
Bacterial Chromatophores↗
Rabbit corneal irrigation as a model system for studies on the relative toxicity of bacterial products implicated in periodontal disease. The toxicity of neutralized ammonia solutions.
Explore the source record for details and available documents.
Ammonia↗
Full-cyclic control strategy of SBR for nitrogen removal in strong wastewater using common sensors.
A full-cyclic automatic control strategy for sequencing batch reactors (SBR) was proposed using only common sensors such as ORP, DO and pH. The main objective was to develop a generally applicable and robust control strategy. To accomplish this, various control schemes found in the literature or suggested by authors were examined at diverse ammonia loads and SCOD/NH4(+)-N ratios. Advantages and constraints of each scheme were discussed and compared. Ammonia load was estimated with DO lag time during the aerobic stage, and then the influent pump was manipulated to meet the desired load at the next anoxic stage. A partial denitrification scheme was chosen for the anoxic stage period control, to save anoxic time and external carbon. For external carbon dosage control, intermittent feeding at each anoxic stage was concluded to be a suitable scheme. The anoxic stage period could be successfully controlled by the combination of pH increase and DO increase. Every suggested control scheme was incorporated into a full-cyclic control strategy and tested at 0.02, 0.035, 0.08 kg NH4(+)-N/m3/sub-cycle. From the results, it is expected to perform unmanned automatic SBR operation with this strategy.
Ammonia↗
Anaerobic digestion of slaughterhouse waste with UF-membrane separation and recycling of permeate after free ammonia stripping.
Anaerobic digestion can adapt to free ammonia to a certain extent. During the anaerobic digestion of slaughterhouse waste, however, an ammonia concentration of up to 15 g Nl(-1) can be reached in the sludge liquid and this will even inhibit adapted sludge. To lower this concentration, a fraction of the digester liquid must therefore be continuously separated from the digested sludge and the free ammonia stripped before the liquid is recycled to the digester. A mesophilic laboratory digester was successfully operated with an ammonium concentration of 4-5g l(-1) and a pH of 8.0-8.4. After free ammonia stripping, the excess liquid was treated in a laboratory SBR for nitrogen and phosphorus removal before being added to the receiving water. The effluent had no toxic effect on daphnia and algae.
Abattoirs↗
Osmoregulatory role of alanine during salt stress in the nitrogen fixing cyanobacterium Anabaena sp. 287.
The freshwater cyanobacterium, Anabaena sp. 287 exhibited enhanced tolerance to NaCl in the presence of ammonium, nitrate, and the amino acids, alanine, valine, proline, lysine, histidine, methionine and aspartic acid. Apart from providing permanent protection to the growth during stress, like NO3- and NH4+, alanine also relieved the initial salt mediated inhibition on enzymes involved in nitrogen fixation, photosynthesis and respiration. The accumulation of sugars was observed only during molecular nitrogen growth in the presence of salt. The cellular total nitrogen content was inversely proportional to the total sugar concentration. All nitrogenous substances which supported growth in the presence of salt curtailed the Na+ influx. Sodium chloride concentration-dependent [3H]D-alanine uptake in this cyanobacterium favours the conclusion that alanine acts as an osmoregulator along with sugars.
Alanine↗
Urea and ammonium removal based on alkalinization and removal of free ammonia.
A novel approach is reported for the removal of ammonium formed from the conversion of urea by urease. By alkalinization, ammonium is converted into free ammonia. Free ammonia can then be very easily removed by a number of approaches: as gaseous ammonia by air bubbling, oxygenator, or air ventilation; by adsorbent for free ammonia; or other approaches.
Adsorption↗
Ketoglutarate tolerance test in liver disease.
Explore the source record for details and available documents.
Ammonia↗
Dynamic transformations of nitrogen during mechanical-biological pre-treatment of municipal solid waste.
Mechanical-biological pre-treatment (MBP) of municipal solid waste (MSW) has gained evidence as a practice capable of accomplishing the requirements for environmental sustainable landfilling. In particular, MBP is effective in reducing the ammoniacal nitrogen content in the leachate. However, few data are available on the modifications of the nitrogen forms occurring during MBP and on the role played by processes such as nitrification and generation of refractory organic compounds. The dynamic transformations of nitrogen were investigated during the MBP. MSW was mechanically and biologically pre-treated; samples were collected at different stages of the process and analysed to investigate the evolution of nitrogen forms; batch and column leaching tests were performed as well. The results indicate that nitrification is negligible and volatilization can only partially explain the low ammoniacal nitrogen content in the leachate. Incorporation of ammoniacal nitrogen into a refractory organic form was assessed and is likely to play an important role. The maximum content of refractory organic nitrogen in the solid waste was achieved after about 60 days of aerobic pre-treatment; therefore, the minimal duration of the MBP should be about 8-9 weeks in order to optimize the ammoniacal nitrogen incorporation, unless the waste is characterized by a low C/N ratio.
Ammonia↗
Tandem mass spectra of ammonium ion, metal ion and ligated metal ion adducts of acyclic sugar derivatives.
The tandem mass (MS/MS) spectra of ammonium ion, metal ion and ligated metal ion adducts of chain-extended acyclic nitro-containing deoxyglucose and deoxygalactose derivatives have been studied. The ammonium adducts fragment primarily by elimination of ammonia followed by acetic acid, thus not giving much structural information. In contrast, cationization of these compounds by metal ions and ligated metal ions gave structurally informative and useful fragment ions on MS/MS. The metal ions and ligated metal ions play an important role in controlling and directing fragmentation. Retro-aldol fragmentation is facilitated by metal ions such as Li(+), Na(+), Ag(+) and Cu(+), whereas the adducts with higher alkali metal ions such as Rb(+) and Cs(+) fragment to give only the corresponding metal ions. The divalent metal ions such as Cu(2+) and Ba(2+) also induce retro-aldol fragmentation. However, the charge is carried by the aldehyde fragment in the case of Cu(2+) adducts, whereas the nitroalkane fragment carries the charge in the case of Ba(2+) adducts. Ligated metal ions such as ZnCl(+), CuCl(+), InCl(2) (+) and BaCl(+) also behave similarly and induce retro-aldol fragmentation in these acyclic sugars. Both the metal ion and ligated metal ion adducts can fragment by elimination of metal-containing neutral molecules.
Acetic Acid↗
The chemical conditions on the parent body of the Murchison meteorite: some conclusions based on amino, hydroxy and dicarboxylic acids.
Amino and hydroxy acids have been identified in the Murchison meteorite. Their presence is consistent with a synthetic pathway involving aldehydes, hydrogen cyanide and ammonia in an aqueous environment (Strecker-cyanohydrin synthesis). From the various equilibrium and rate constants involved in this synthesis, four independent estimates of the ammonium ion concentrations on the parent body at the time of compound synthesis are obtained; all values are about 2 x 10(-3) M. Succinic acid and beta-alanine have also been detected in the Murchison meteorite. Their presence is consistent with a synthesis from acrylonitrile, hydrogen cyanide and ammonia. Using the equilibrium and rate constants for this synthetic pathway, and the succinic acid/beta-alanine ratio measured in the Murchison meteorite, an estimate of the hydrogen cyanide concentration of 10(-3) to 10(-2) M is obtained. Since hydrogen cyanide hydrolyzes relatively rapidly in an aqueous environment (t1/2 < 10(4) yrs) this high concentration implies a period of synthesis of organic compounds as short as 10(4) years on the Murchison meteorite parent body.
Acrylonitrile↗
Synthesis and biological evaluation of certain 2'-deoxy-beta-D-ribo- and -beta-D-arabinofuranosyl nucleosides of purine-6-carboxamide and 4,8-diaminopyrimido[5,4-d]pyrimidine.
The key intermediate 9-(2,3,5,-tri-O-acetyl-beta-D-arabinofuranosyl)purine-6-carbonitrile (7) was synthesized in four steps from 9-beta-D-arabinofuranosylpurine-6-thione (3) via 6-(methylsulfonyl)-9-(2,3,5-tri-O-acetyl-beta-D-arabinofuranosyl)purine (6). Reaction of compound 7 with methanolic ammonia provided the rearranged compound 4-amino-8-(beta-D-arabinofuranosylamino)pyrimido[5,4-d]pyrimidine (8). Treatment of 7 with ammonium hydroxide and hydrogen peroxide provided 9-beta-D-arabinofuranosylpurine-6-carboxamide (9). Compound 7 was also treated with sodium hydrosulfide to yield 9-beta-D-arabinofuranosylpurine-6-thiocarboxamide (10). Similarly, 9-(2-deoxy-3,5-di-O-acetyl-beta-D-erythro-pentofuranosyl)purine 6-carbonitrile (17) was prepared from 6-chloro-9-(2-deoxy-beta-D-erythro-pentofluranosyl)purine (11) via 9-(2-deoxy-beta-D-erythro-pentofuranosyl)purine-6-thione. Compound 17 was converted into 4-amino-8-[(2-deoxy-beta-D-erythro-pentofuranosyl)amino]pyrimido[5,4-d]pyrimidi ne (18) and 9-(2-deoxy-beta-D-erythro-pentofuranosyl)purine-6-carboxamide (20), respectively. Compound 2 showed immunosuppressive activity and also inhibited the growth of L-1210 leukemia in mice. Arabinonucleoside analogues 8-10 were inactive when tested against RNA and DNA viruses in cell culture.
Animals↗
Developing seasonal ammonia emission estimates with an inverse modeling technique.
Significant uncertainty exists in magnitude and variability of ammonia (NH3) emissions, which are needed for air quality modeling of aerosols and deposition of nitrogen compounds. Approximately 85% of NH3 emissions are estimated to come from agricultural nonpoint sources. We suspect a strong seasonal pattern in NH 3 emissions; however, current NH3 emission inventories lack intra-annual variability. Annually averaged NH 3 emissions could significantly affect model-predicted concentrations and wet and dry deposition of nitrogen-containing compounds. We apply a Kalman filter inverse modeling technique to deduce monthly NH3 emissions for the eastern U.S. Final products of this research will include monthly emissions estimates from each season. Results for January and June 1990 are currently available and are presented here. The U.S. Environmental Protection Agency (USEPA) Community Multiscale Air Quality (CMAQ) model and ammonium (NH4+) wet concentration data from the National Atmospheric Deposition Program (NADP) network are used. The inverse modeling technique estimates the emission adjustments that provide optimal modeled results with respect to wet NH4+ concentrations, observational data error, and emission uncertainty. Our results suggest that annual average NH 3 emissions estimates should be decreased by 64% for January 1990 and increased by 25% for June 1990. These results illustrate the strong differences that are anticipated for NH3 emissions.
Agriculture↗
Ammonia Assimilation in the Roots of Nitrate- and Ammonia-Grown Hordeum Vulgare (cv Golden Promise).
(15)N kinetic labeling studies were performed on seedlings of Hordeum vulgare L. var. Golden Promise growing under steady state conditions. Patterns of label incorporation in the pools of nitrogen compounds of roots fed [(15)N]ammonium were compared with computer-simulated labeling curves. The data were found to be quantitatively consistent with a three-compartment model in which ammonium is assimilated solely into the amide-N of glutamine. Labeling data from roots fed [(15)N]nitrate were also found to be at least qualitatively consistent with the assimilation of ammonia into glutamine. Methionine sulfoximine almost completely blocked the incorporation of (15)N label into the amino acid pools of barley roots fed [(15)N]nitrate. These observations suggest that ammonia assimilation occurs solely via the glutamine synthetase/glutamate synthase pathway in both nitrate- and ammonia-grown barley roots.
Journal Article↗
Regulation of ammonia uptake in aspergillus nidulans.
The ammonia uptake in A. nidulans was found to be linear for about 20 min, and was proportional up to 1.5 mg/ml dry cell density. The transport of ammonia does not involve energy. Normal and biotin deficient A. nidulans showed an identical Km-values of 10.26 X 10(-5) M ammonia for uptake. The uptake of ammonium ion has been shown to be regulated by the intracellular concentration of ammonia.
Aspergillus nidulans↗
Protective effect of L-carnitine in ammonia-precipitated encephalopathy in the portacaval shunted rat.
L-carnitine administration prevents the neurological symptoms of acute ammonia toxicity. To further evaluate its efficacy in the prevention of hepatic encephalopathy in hyperammonemic conditions, L-carnitine (16 mmol/kg, intraperitoneally [i.p.] was administered 1 hour before ammonium acetate (NH4OAc) (8.5 mmol/kg, subcutaneously) to portacaval shunted (PCS) rats. Cerebrospinal fluid (CSF) ammonia, lactate, and amino acid levels were measured in relation to deteriorating neurological status in these animals. None of 35 L-carnitine-treated animals showed neurological deterioration after NH4OAC administration compared with saline-treated controls; the latter manifested severe encephalopathy progressing through loss of righting reflex to coma. Survival rate was 100% in the L-carnitine-treated group compared with 5% in saline-treated controls. Following NH4OAC administration to PCS rats, CSF ammonia increased to 0.93 +/- 0.15 mmol/L and 1.24 +/- 0.15 mmol/L at precoma and coma stages of encephalopathy (P < .01) respectively. Treatment with L-carnitine reduced CSF ammonia at both precoma and coma stages; the time-course of this protective effect paralleled blood and CSF L-carnitine accumulation. CSF alanine and lactate increases following NH4OAC administration to PCS rats were significantly attenuated following L-carnitine treatment. However, L-carnitine treatment did not lead to significant reductions in plasma ammonia nor CSF or brain glutamine in these animals. These findings show the therapeutic efficacy of L-carnitine in ammonia-precipitated coma in PCS rats and suggest that this protective effect is centrally mediated involving improved mitochondrial respiration. L-carnitine could be of therapeutic benefit in the prevention of hepatic encephalopathy precipitated by ammoniagenic conditions in humans with chronic liver disease.
Amino Acids↗