Effects of Methionine Sulfoximine and Glycine on Nitrogen Metabolism of Maize Leaves in the Light

1983 ◽  
Vol 10 (2) ◽  
pp. 187 ◽  
Author(s):  
MG Berger ◽  
HP Fock
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Glutamine Synthetase ◽  
Nitrogen Cycling ◽  
Co2 Assimilation ◽  
Methionine Sulfoximine ◽  
Co2 Evolution ◽  
Ammonia Content ◽  
Ammonia Accumulation ◽  
Maize Leaves

Detached maize leaves with their cut bases in water or in solutions containing 15 mM [14C, 15N]glycine, 15 mM [14C]glutamate, 5 mM methionine sulfoximine (an inhibitor of glutamine synthetase) or the appropriate amino acid plus inhibitor, were incubated for up to 135 min in the light. The concentrations and the 15N content of ammonia and of amino acids involved in photorespiratory nitrogen cycling were determined. Incubation with methionine sulfoximine or glycine increased the ammonia content significantly, whereas glutamate showed no effect. The nitrogen of glycine was metabolized into serine and ammonia. Ammonia was first recycled into glutamine, and then into glutamate. The glycine carbon skeleton served as a precursor for serine. Based on the data for ammonia accumulation the minimum rate of photorespiratory CO2 evolution in maize leaves was estimated to be about 1% of the rate of CO2 assimilation.

scholarly journals 2235 15N-Leucine transport across the blood brain barrier is significantly impaired in the glutamine synthetase-inhibited brain

2018 ◽  
Vol 2 (S1) ◽  
pp. 1-1
Author(s):  
Shaun E. Gruenbaum ◽  
Roni Dhaher ◽  
Kevin Behar ◽  
Hitten Zaveri ◽  
Mark Erfe ◽  
...  
Keyword(s):  
Amino Acid ◽  
Glutamine Synthetase ◽  
Dentate Gyrus ◽  
Extracellular Fluid ◽  
Ultra Performance Liquid Chromatography ◽  
Methionine Sulfoximine ◽  
Causative Role ◽  
Immune System Dysfunction ◽  
Tightly Coupled ◽  
The Brain

OBJECTIVES/SPECIFIC AIMS: Astroglial glutamine synthetase (GS), which metabolizes glutamate and ammonia to glutamine, is critical for the detoxification of brain ammonia, clearance of synaptic glutamate, and production of brain glutamine. Perturbations in the expression and activity of GS are thought to play a causative role in the pathogenesis of several conditions of abnormal neurotransmission. Although the long-term consequences of GS inhibition on amino acid homeostasis in the brain are unknown, it is thought that amino acid influx in the brain is tightly coupled with glutamine efflux via the L-type amino acid transporter. Both glutamine and leucine serve many critical functions in the brain including protein synthesis, gene expression, insulin regulation, and immune signaling. The objective of this study was to determine the effects of chronic GS inhibition with methionine sulfoximine (MSO) on glutamine and leucine homeostasis in the brain. METHODS/STUDY POPULATION: In total, 12 rats were surgically implanted with microdialysis guide cannulas in the bilateral dentate gyrus. Rats were randomly divided for surgical implantation of either a MSO (n=6) or phosphate buffer saline (PBS; n=6) pump in the right dentate gyrus. After 7 days, bilateral microdialysis probes were placed under brief isoflurane anesthesia, and microdialysis flow was established by infusing 0.5 µL/min of artificial extracellular fluid. Dialysate samples were collected every 30 minutes for the duration of the experiment. A 113 mM 15N-Leucine (3.6 mL/h) and 2 M 2–13C-sodium acetate (0.0633 μL/g/min for t=0–5 min, 0.0316 μL/g/min for t=5–10 min, and 0.0253 μL/g/min for t>10 min) solution was infused intravenously for 300 minutes. The EZ:Faast Free Amino Acid analysis kit and ultra-performance liquid chromatography/tandem mass spectrometry was used for quantification of amino acids in the dialysate fluid. RESULTS/ANTICIPATED RESULTS: At baseline (t=0 h), the concentrations of glutamine were significantly lower in MSO-treated rats (p<0.001) in the ipsilateral (GS-inhibited) hippocampus. There were no differences in glutamine concentrations between MSO and PBS-treated rats in the contralateral hippocampus. In PBS-treated rats, there was a significant increase in 15N-leucine between t=0 hour and t=5 hour in the contralateral (p<0.05) and ipsilateral (p<0.05) hippocampus. In MSO-treated rats, there was a significant increase in 15N-leucine between t=0 and t=5 hours in the contralateral (p<0.05) hippocampus, but not in the ipsilateral hippocampus (p=ns.). DISCUSSION/SIGNIFICANCE OF IMPACT: This study demonstrated for the first time that basal glutamine concentrations are low in areas of the brain where GS is acutely inhibited, and that leucine uptake in these brain areas are markedly decreased. Perturbations in glutamine and leucine homeostasis have been implicated in several disease processes including diabetes, obesity, liver disease, immune system dysfunction, epilepsy, and cancer, and the glutamine-dependent leucine influx in the brain may be a novel and important therapeutic target to treat these conditions.

Degradation of glutamine synthetase in intact chloroplasts isolated from pea (Pisum sativum) leaves

1998 ◽  
Vol 25 (3) ◽  
pp. 279 ◽  
Author(s):  
Melanie Thoenen ◽  
Urs Feller
Keyword(s):  
Pisum Sativum ◽  
Glutamine Synthetase ◽  
Active Oxygen Species ◽  
Co2 Assimilation ◽  
Methionine Sulfoximine ◽  
General Effect ◽  
Chloroplast Proteins ◽  
Intact Chloroplasts ◽  
The Stability ◽  
Stromal Proteins

Chloroplast proteins can be degraded in the intact organelle, but the relative rates of degradation vary considerably. To investigate regulatory aspects of glutamine synthetase (GS) degradation, isolated pea (Pisum sativum L.) chloroplasts were used as a suitable system. Since chloroplasts were re-isolated after incubation, only chloroplasts remaining intact throughout the incubation and processes occurring therein were analysed. Net changes of nuclear-encoded proteins indicate degradation because protein synthesis is no longer possible under these conditions. Incubation of intact chloroplasts in a medium which promotes CO2 -assimilation led to the stabilisation of GS and several other chloroplast proteins. This general effect suggests that photosynthetic metabolism is relevant for the stability of stromal proteins. In addition, GS was specifically stabilised by methionine sulfoximine (MSO), a potent inhibitor of GS. However, other enzymes tested were not affected by MSO. When chloroplasts were incubated with methyl viologen, the degradation of several stromal enzymes including GS was accelerated, most likely by active oxygen species. Again, MSO specifically delayed the degradation of GS. As MSO is a substrate analogue, it appears likely that substrates or other ligands influence the susceptibility of enzymes against degradation systems present in the same compartment.

Biochemical interactions between the symbionts of Convoluta roscoffensis

1975 ◽  
Vol 189 (1094) ◽  
pp. 121-135 ◽  
Keyword(s):  
Amino Acids ◽  
Uric Acid ◽  
Lactic Acid ◽  
Amino Acid ◽  
Glutamine Synthetase ◽  
Excess Oxygen ◽  
Convoluta Roscoffensis

Convoluta will slowly eject most of their algae if CO 2 is bubbled through their seawater media for a brief preliminary period. By means of this technique, it was shown that at least half of the carbon fixed in photosynthesis moved from alga to animal, possibly in the form of amino acids. Dichlorophenyldimethyl urea completely inhibits photosynthesis in intact worms, but causes no other immediate damage to the animals. No uric acid can be detected in healthy animals, but it accumulates after 2 weeks’ incubation in DCMU. Uricase and glutamine synthetase are both detectable in worms, and it is suggested that ammonia produced by uric acid catabolism in algae is assimilated into glutamine, which may be the main amino acid released back to the animal. If animals are first labelled with a pulse of 14 C through photosynthesis and then transferred to nonradioactive seawater containing 1 g/100 ml alanine, the amount of fixed 14 C released from worms is increased by darkness or DCMU treatment with much of the released 14 C appearing in lactic acid; these effects are largely abolished if excess oxygen is supplied to the worms. This suggests that photosynthetically produced oxygen may be utilized by animals, but since they survived 4 weeks in DCMU, it was clearly not essential.

scholarly journals Effects of inhibiting glutamine synthetase and blocking glutamate uptake on b-wave generation in the isolated rat retina

1999 ◽  
Vol 16 (2) ◽  
pp. 345-353 ◽  
Author(s):  
BARRY S. WINKLER ◽  
NATALIA KAPOUSTA-BRUNEAU ◽  
MATTHEW J. ARNOLD ◽  
DANIEL G. GREEN
Keyword(s):  
Amino Acids ◽  
Glutamine Synthetase ◽  
Glutamate Uptake ◽  
Müller Cells ◽  
Glutamate Transporters ◽  
Methionine Sulfoximine ◽  
Muller Cells ◽  
Rat Retina ◽  
Subsequent Conversion ◽  
Isolated Rat

The purpose of the present experiments was to evaluate the contribution of the glutamate-glutamine cycle in retinal glial (Müller) cells to photoreceptor cell synaptic transmission. Dark-adapted isolated rat retinas were superfused with oxygenated bicarbonate-buffered media. Recordings were made of the b-wave of the electroretinogram as a measure of light-induced photoreceptor to ON-bipolar neuron transmission. L-methionine sulfoximine (1–10 mM) was added to superfusion media to inhibit glutamine synthetase, a Müller cell specific enzyme, by more than 99% within 5–10 min, thereby disrupting the conversion of glutamate to glutamine in the Müller cells. Threo-hydroxyaspartic acid and D-aspartate were used to block glutamate transporters. The amplitude of the b-wave was well maintained for 1–2 h provided 0.25 mM glutamate or 0.25 mM glutamine was included in the media. Without exogenous glutamate or glutamine the amplitude of the b-wave declined by about 70% within 1 h. Inhibition of glutamate transporters led to a rapid (2–5 min) reversible loss of the b-wave in the presence and absence of the amino acids. In contrast, inhibition of glutamine synthetase did not alter significantly either the amplitude of the b-wave in the presence of glutamate or glutamine or the rate of decline of the b-wave found in the absence of these amino acids. Excellent recovery of the b-wave was found when 0.25 mM glutamate was resupplied to L-methionine sulfoximine–treated retinas. The results suggest that in the isolated rat retina uptake of released glutamate into photoreceptors plays a more important role in transmitter recycling than does uptake of glutamate into Müller cells and its subsequent conversion to glutamine.

scholarly journals Implication of the glutamine synthetase/glutamate synthase pathway in conditioning the amino acid metabolism in bundle sheath and mesophyll cells of maize leaves

FEBS Journal ◽  
2008 ◽  
Vol 275 (12) ◽  
pp. 3193-3206 ◽  
Author(s):  
Marie-Hélène Valadier ◽  
Ayako Yoshida ◽  
Olivier Grandjean ◽  
Halima Morin ◽  
Jocelyne Kronenberger ◽  
...  
Keyword(s):  
Amino Acid ◽  
Glutamine Synthetase ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Glutamate Synthase ◽  
Bundle Sheath ◽  
Mesophyll Cells ◽  
Maize Leaves

scholarly journals Effect of Glutamine Synthetase Inhibition on Brain and Interorgan Ammonia Metabolism in Bile Duct Ligated Rats

2013 ◽  
Vol 34 (3) ◽  
pp. 460-466 ◽  
Author(s):  
Andreas W Fries ◽  
Sherry Dadsetan ◽  
Susanne Keiding ◽  
Lasse K Bak ◽  
Arne Schousboe ◽  
...  
Keyword(s):  
Amino Acids ◽  
Bile Duct ◽  
Glutamine Synthetase ◽  
Methionine Sulfoximine ◽  
Ammonia Metabolism ◽  
Liver And Kidney ◽  
Glutamine Synthesis ◽  
Alanine Synthesis ◽  
High Concentrations ◽  
The Brain

Ammonia has a key role in the development of hepatic encephalopathy (HE). In the brain, glutamine synthetase (GS) rapidly converts blood-borne ammonia into glutamine which in high concentrations may cause mitochondrial dysfunction and osmolytic brain edema. In astrocyte-neuron cocultures and brains of healthy rats, inhibition of GS by methionine sulfoximine (MSO) reduced glutamine synthesis and increased alanine synthesis. Here, we investigate effects of MSO on brain and interorgan ammonia metabolism in sham and bile duct ligated (BDL) rats. Concentrations of glutamine, glutamate, alanine, and aspartate and incorporation of 15NH4+ into these amino acids in brain, liver, muscle, kidney, and plasma were similar in sham and BDL rats treated with saline. Methionine sulfoximine reduced glutamine concentrations in liver, kidney, and plasma but not in brain and muscle; MSO reduced incorporation of 15NH4+ into glutamine in all tissues. It did not affect alanine concentrations in any of the tissues but plasma alanine concentration increased; incorporation of 15NH4+ into alanine was increased in brain in sham and BDL rats and in kidney in sham rats. It inhibited GS in all tissues examined but only in brain was an increased incorporation of 15N-ammonia into alanine observed. Liver and kidney were important for metabolizing blood-borne ammonia.

Nonparticipation of extracellular glutathione in renal transport of dibasic amino acids

1979 ◽  
Vol 57 (10) ◽  
pp. 1168-1171 ◽  
Author(s):  
André G. Craan ◽  
Michel Bergeron
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Proximal Tubules ◽  
Methionine Sulfoximine ◽  
Acid Transport ◽  
Intracellular Glutathione ◽  
Direct Competition ◽  
Dibasic Amino Acid ◽  
Dibasic Amino Acids

Microinjections of L-[14C]arginine (2.9 mM) and L-[14C]ornithine (3.4 mM) were made into renal proximal tubules of rats in the presence of methionine sulfoximine (MSO) (10, 20 mM), ATP (10 mM), and MgCl2 (20 mM) together. Absorption of both labelled amino acids dropped, respectively, by 31.1 and 49.1% compared with control microinjections. The MSO alone or ATP plus MgCl2 had no effect. These data suggest that the inhibition by MSO plus ATP plus MgCl2 is not due to direct competition between MSO and dibasic amino acids but rather to suppression of the renewal of intracellular glutathione. Such an effect is discussed in comparison with cycloleucine inhibition of dibasic amino acid transport. Addition of exogenous glutathione to microinjectates did not reverse either type of inhibition. This study shows that while intracellular glutathione may affect amino acid transport, extracellular glutathione has no effect.

The Effect of Phosphinothricin on the Assimilation of Ammonia in Plants

1984 ◽  
Vol 39 (5) ◽  
pp. 500-504 ◽  
Author(s):  
Aloysius Wild ◽  
Remigius Manderscheid
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Photosynthetic Activity ◽  
Light Period ◽  
Methionine Sulfoximine ◽  
Nitrogen Compounds ◽  
Strong Reduction ◽  
Strong Inhibitor ◽  
Ammonia Accumulation

The effects of ᴅʟ-phosphinothricin and L-methionine sulfoximine on the enzymes of nitrogen assimilation were studied. Furthermore we investigated the accumulation of ammonia and the photosynthetic activity after the treatment of mustard plants with phosphinothricin. Phosphino-thricin was a specific and very strong inhibitor of glutamine synthetase. Major differences, however, were found between the phosphinothricin affinity of the leaf enzyme and that of the root of mustard plants. The leaf enzyme was 50% inhibited at a concentration of 10-4 m phosphinothricin (pI50 = 4), whereas the root enzyme already showed the same effect at a concentration of 2 × 10-5m (pI50 = 4.7). In addition Ki values of about 0.03 mм for the leaf enzyme and 0.002 mм for the root enzyme respectively were determined. Phosphinothricin treatment of plants caused an ammonia accumulation in tissues. The accumulation was light dependent. At the beginning of the light period the major sources of ammonia accumulation could be the nitrogen assimilation as well as catabolic processes of nitrogen compounds. A clear contribution of photorespiration was only found when higher concentrations of ammonia were reached. The application of phosphinothricin induced a strong reduction of CO2 assimilation.

scholarly journals Amino acid derivatives of natural chlorins as a platform for the creation of targeted photosensitizers in oncology

2021 ◽  
Vol 15 (6) ◽  
pp. 16-33
Author(s):  
A. F. Mironov ◽  
P. V. Ostroverkhov ◽  
S. I. Tikhonov ◽  
V. A. Pogorilyy ◽  
N. S. Kirin ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Tumor Cells ◽  
Targeted Delivery ◽  
Methionine Sulfoximine ◽  
Amino Acid Derivatives ◽  
Resonance Spectroscopy ◽  
Biochemical Processes ◽  
Derivatives Of

Objectives. This study aims to obtain the amino acid derivatives of chlorophyll a and bacteriochlorophyll a for the targeted delivery of pigments to tumor foci. This will increase biocompatibility and, as a result, reduce toxic side effects. In addition to photodynamic efficiency, an additional cytotoxic effect is expected for the obtained conjugates of photosensitizers (PSs) with amino acids. This is owing to the participation of the latter in intracellular biochemical processes, including interaction with the components of the glutathione antioxidant system, leading to the vulnerability of tumor cells to oxidative stress.Methods. In this work, we have implemented the optimization of the structure of a highly efficient infrared PS based on O-propyloxim-N-propoxybacteriopurpurinimide (DPBP), absorbing at 800 nm and showing photodynamic efficacy for the treatment of deep-seated and pigmented tumors, by introducing L-lysine, L-arginine, methionine sulfoximine (MSO), and buthionine sulfoximine (BSO) methyl esters. The structure of the obtained compounds was proved by mass spectrometry and nuclear magnetic resonance spectroscopy, and the photoinduced cytotoxicity was studied in vitro on the HeLa cell line.Results. Conjugates of DPBP with amino acids and their derivatives, such as lysine, arginine, MSO, and BSO have been prepared. The chelating ability of DPBP conjugate with lysine was shown, and its Sn(IV) complex was obtained.Conclusions. Biological testing of DPBP with MSO and BSO showed a 5–6-fold increase in photoinduced cytotoxicity compared to the parent DPBP PS. Additionally, a high internalization of pigments by tumor cells was found, and the dark cytotoxicity (in the absence of irradiation) of DPBP-MSO and DPBP-BSO increased fourfold compared to the initial DPBP compound. This can be explained by the participation of methionine derivatives in the biochemical processes of the tumor cell.

scholarly journals Synergistic Regulation of Nitrogen and Sulfur on Redox Balance of Maize Leaves and Amino Acids Balance of Grains

2020 ◽  
Vol 11 ◽  
Author(s):  
Shuoran Liu ◽  
Shuai Cui ◽  
Xue Zhang ◽  
Yin Wang ◽  
Guohua Mi ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Nutritional Quality ◽  
Protein Concentration ◽  
Maize Yield ◽  
Redox Balance ◽  
Essential Amino Acids ◽  
Grain Protein ◽  
Grain Protein Concentration ◽  
Maize Leaves

As a primary food crop, maize is widely grown around the world. However, the deficiency of essential amino acids, such as lysine, tryptophan, and methionine, results in poor nutritional quality of maize. In addition, the protein concentration of maize declines with the increase in yield, which further reduces the nutritional quality. Here, the photosynthesis of leaves, grain amino acid composition, and stoichiometry of N and S are explored. The results show that N and S maintained the redox balance by increasing the content of glutathione in maize leaves, thereby enhancing the photosynthetic rate and maize yield. Simultaneously, the synergy of N and S increased the grain protein concentration and promoted amino acid balance by increasing the cysteine concentration in maize grains. The maize yield, grain protein concentration, and concentration of essential amino acids, such as lysine, tryptophan, and methionine, could be simultaneously increased in the N:S ratio range of 11.0 to 12.0. Overall, the synergy of N and S simultaneously improved the maize yield and nutritional quality by regulating the redox balance of maize leaves and the amino acids balance of grains, which provides a new theoretical basis and practical method for sustainable production of maize.

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