scholarly journals De novo amino acid synthesis and turnover during N2 fixation

2017 ◽  
Vol 63 (3) ◽  
pp. 1076-1092 ◽  
Author(s):  
Natalie Loick-Wilde ◽  
Sarah C. Weber ◽  
Elvita Eglite ◽  
Iris Liskow ◽  
Detlef Schulz-Bull ◽  
...  
2020 ◽  
Vol 61 (6) ◽  
pp. 1028-1040
Author(s):  
Dan Pereksta ◽  
Dillon King ◽  
Fahmida Saki ◽  
Amith Maroli ◽  
Elizabeth Leonard ◽  
...  

Abstract Cellular homeostasis is maintained by the proteasomal degradation of regulatory and misfolded proteins, which sustains the amino acid pool. Although proteasomes alleviate stress by removing damaged proteins, mounting evidence indicates that severe stress caused by salt, metal(oids), and some pathogens can impair the proteasome. However, the consequences of proteasome inhibition in plants are not well understood and even less is known about how its malfunctioning alters metabolic activities. Lethality causes by proteasome inhibition in non-photosynthetic organisms stem from amino acid depletion, and we hypothesized that plants respond to proteasome inhibition by increasing amino acid biosynthesis. To address these questions, the short-term effects of proteasome inhibition were monitored for 3, 8 and 48 h in the roots of Brassica napus treated with the proteasome inhibitor MG132. Proteasome inhibition did not affect the pool of free amino acids after 48 h, which was attributed to elevated de novo amino acid synthesis; these observations coincided with increased levels of sulfite reductase and nitrate reductase activities at earlier time points. However, elevated amino acid synthesis failed to fully restore protein synthesis. In addition, transcriptome analysis points to perturbed abscisic acid signaling and decreased sugar metabolism after 8 h of proteasome inhibition. Proteasome inhibition increased the levels of alternative oxidase but decreased aconitase activity, most sugars and tricarboxylic acid metabolites in root tissue after 48 h. These metabolic responses occurred before we observed an accumulation of reactive oxygen species. We discuss how the metabolic response to proteasome inhibition and abiotic stress partially overlap in plants.


2018 ◽  
Vol 30 (10) ◽  
pp. 2240.1-2254 ◽  
Author(s):  
Umarah Mubeen ◽  
Jessica Jüppner ◽  
Jessica Alpers ◽  
Dirk K. Hincha ◽  
Patrick Giavalisco

2010 ◽  
Vol 76 (5) ◽  
pp. 1507-1515 ◽  
Author(s):  
Motoyuki Shimizu ◽  
Tatsuya Fujii ◽  
Shunsuke Masuo ◽  
Naoki Takaya

ABSTRACT Although branched-chain amino acids are synthesized as building blocks of proteins, we found that the fungus Aspergillus nidulans excretes them into the culture medium under hypoxia. The transcription of predicted genes for synthesizing branched-chain amino acids was upregulated by hypoxia. A knockout strain of the gene encoding the large subunit of acetohydroxy acid synthase (AHAS), which catalyzes the initial reaction of the synthesis, required branched-chain amino acids for growth and excreted very little of them. Pyruvate, a substrate for AHAS, increased the amount of hypoxic excretion in the wild-type strain. These results indicated that the fungus responds to hypoxia by synthesizing branched-chain amino acids via a de novo mechanism. We also found that the small subunit of AHAS regulated hypoxic branched-chain amino acid production as well as cellular AHAS activity. The AHAS knockout resulted in higher ratios of NADH/NAD+ and NADPH/NADP+ under hypoxia, indicating that the branched-chain amino acid synthesis contributed to NAD+ and NADP+ regeneration. The production of branched-chain amino acids and the hypoxic induction of involved genes were partly repressed in the presence of glucose, where cells produced ethanol and lactate and increased levels of lactate dehydrogenase activity. These indicated that hypoxic branched-chain amino acid synthesis is a unique alternative mechanism that functions in the absence of glucose-to-ethanol/lactate fermentation and oxygen respiration.


Metabolism ◽  
1982 ◽  
Vol 31 (12) ◽  
pp. 1210-1218 ◽  
Author(s):  
Jean-Jacques Robert ◽  
Dennis M. Bier ◽  
X.H. Zhao ◽  
Dwight E. Matthews ◽  
Vernon R. Young

2005 ◽  
Vol 32 (9) ◽  
pp. 831 ◽  
Author(s):  
Bok-Rye Lee ◽  
Woo-Jin Jung ◽  
Kil-Yong Kim ◽  
Jean-Christophe Avice ◽  
Alain Ourry ◽  
...  

In white clover (Trifolium repens L. cv. Regal) the kinetics of de novo synthesis of amino acid and protein were compared by tracing 15N under well-watered (control) or water-deficit conditions. The physiological relationship between ammonia concentration, in response to the change in leaf water parameters, and de novo synthesis of amino acid and protein was also assessed. Leaf and root dry mass were not significantly affected for the first 3 d, whereas metabolic parameters such as total N and ammonia were significantly affected within the first day of water-deficit treatment. Inhibitory effect of water deficit on N acquisition from the soil was significant throughout the experimental period. Water deficit induced a significant increase in ammonia concentration in leaves during the first 3 d, and in roots for only the first day. In both leaves and roots, an increase in de novo amino acid synthesis, which peaked in leaves within the first 3 d of water-deficit treatment (Ψw ≥ –1.18 MPa), was observed. The rate of decrease in de novo protein synthesis gradually accelerated as the duration of the water-deficit treatment increased. There was a significant positive relationship between ammonia production and the increase in de novo amino acid synthesis during the first 3-d period, but not during the later period (day 3–day 7). This experiment clearly indicates that the increase in de novo amino acid synthesis caused by water deficit is a transient adaptive response occurring during the first few days and that it is associated with the increased ammonia concentrations, which in turn arise in response to a decrease in de novo protein synthesis.


Diabetes ◽  
1985 ◽  
Vol 34 (1) ◽  
pp. 67-73 ◽  
Author(s):  
J. J. Robert ◽  
B. Beaufrere ◽  
J. Koziet ◽  
J. F. Desjeux ◽  
D. M. Bier ◽  
...  

1999 ◽  
Vol 45 (2) ◽  
pp. 185-189 ◽  
Author(s):  
Linda E McHolland ◽  
Daniel R Caldwell

Partially purified Anaplasma marginale initial bodies were cultivated in a cell-free system in the presence of [3-14C]pyruvate for 24 or 48 h. Experiments showed that a significant portion of the pyruvate supplied to the cultures was incorporated into initial body components. Label incorporation was reduced by 72% in the presence of oxytetracycline. Fractionation and chromatography of the organisms revealed radioactive incorporation as alanine. This is the first report of de novo amino acid synthesis by A. marginale demonstrating that the rickettsia is capable of using pyruvate, an erythrocyte glycolytic product, in its metabolism.Key words: Anaplasma marginale, pyruvate metabolism, amino acid synthesis.


Diabetes ◽  
1985 ◽  
Vol 34 (1) ◽  
pp. 67-73 ◽  
Author(s):  
J. J. Robert ◽  
B. Beaufrere ◽  
J. Koziet ◽  
J. F. Desjeux ◽  
D. M. Bier ◽  
...  

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Yuko Takizawa ◽  
Yoshinori Takano ◽  
Bohyung Choi ◽  
Prarthana S. Dharampal ◽  
Shawn A. Steffan ◽  
...  

Abstract Stable nitrogen (15N/14N) and carbon (13C/12C) isotopic compositions of amino acids in organisms have widely been employed as a powerful tool to evaluate resource utilization and trophic connection among organisms in diverse ecosystems. However, little is known about the physiological factors or mechanisms responsible for determining the isotopic discrimination (particularly for carbon) within amino acids of organisms. In the present study, we investigated the inter-trophic discrimination of nitrogen and carbon isotopes within amino acids (Δδ15NAA and Δδ13CAA, respectively) using four consumer–diet pairs. Each pairing illustrates a metabolic perspective of isotopic fractionation of amino acids. The Δδ15NAA values in these combinations reveal a trend consistent with those observed in many other combinations in previous studies. This further validates a standard scenario: the deamination preferentially removes 14N amino group from diet-derived amino acids, leaving behind the 15N-enriched amino acids in consumer biomass. The Δδ15NAA values thus mirror the activity of amino acid deamination in consumers. In contrast, the trends in the Δδ13CAA value suggest a different metabolic fate for the amino acid carbon isotope. Based on our results, we predict the following scenario: decarboxylation preferentially removes 12C α-carbon (i.e., carbonyl-carbon) from pyruvic acid in glycolysis, and from α-ketoglutaric acid in the tricarboxylic acid cycle, leaving behind the 13C-enriched both pyruvic and α-ketoglutaric acids. The 13C is then transferred to amino acids that are synthesized from the 13C-enriched precursor molecules within consumers. The Δδ13CAA values therefore mirror the pathways of de novo amino acid synthesis in consumers. The proposed link between nitrogen and carbon isotopes can refine our knowledge of the potential processes affecting the isotopic fractionation within diet and consumer compartments, as well as environmental samples. Graphical abstract


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