scholarly journals Amino Acid Metabolism in Apicomplexan Parasites

Metabolites ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 61
Author(s):  
Aarti Krishnan ◽  
Dominique Soldati-Favre
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Current Knowledge ◽  
Acid Biosynthesis ◽  
Apicomplexan Parasites ◽  
Obligate Intracellular ◽  
Metabolic Functions ◽  
Transcriptomics Data

Obligate intracellular pathogens have coevolved with their host, leading to clever strategies to access nutrients, to combat the host’s immune response, and to establish a safe niche for intracellular replication. The host, on the other hand, has also developed ways to restrict the replication of invaders by limiting access to nutrients required for pathogen survival. In this review, we describe the recent advancements in both computational methods and high-throughput –omics techniques that have been used to study and interrogate metabolic functions in the context of intracellular parasitism. Specifically, we cover the current knowledge on the presence of amino acid biosynthesis and uptake within the Apicomplexa phylum, focusing on human-infecting pathogens: Toxoplasma gondii and Plasmodium falciparum. Given the complex multi-host lifecycle of these pathogens, we hypothesize that amino acids are made, rather than acquired, depending on the host niche. We summarize the stage specificities of enzymes revealed through transcriptomics data, the relevance of amino acids for parasite pathogenesis in vivo, and the role of their transporters. Targeting one or more of these pathways may lead to a deeper understanding of the specific contributions of biosynthesis versus acquisition of amino acids and to design better intervention strategies against the apicomplexan parasites.

scholarly journals BIOSYNTHESIS IN ISOLATED ACETABULARIA CHLOROPLASTS

1972 ◽  
Vol 54 (2) ◽  
pp. 279-294 ◽  
Author(s):  
David C. Shephard ◽  
Wendy B. Levin
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Technical Problems ◽  
Hydrolyzed Protein ◽  
Protein Amino Acids ◽  
Amino Acid Labeling ◽  
Labeling Pattern

The ability of chloroplasts isolated from Acetabulana mediterranea to synthesize the protein amino acids has been investigated. When this chloroplast isolate was presented with 14CO2 for periods of 6–8 hr, tracer was found in essentially all amino acid species of their hydrolyzed protein Phenylalanine labeling was not detected, probably due to technical problems, and hydroxyproline labeling was not tested for The incorporation of 14CO2 into the amino acids is driven by light and, as indicated by the amount of radioactivity lost during ninhydrin decarboxylation on the chromatograms, the amino acids appear to be uniformly labeled. The amino acid labeling pattern of the isolate is similar to that found in plastids labeled with 14CO2 in vivo. The chloroplast isolate did not utilize detectable amounts of externally supplied amino acids in light or, with added adenosine triphosphate (ATP), in darkness. It is concluded that these chloroplasts are a tight cytoplasmic compartment that is independent in supplying the amino acids used for its own protein synthesis. These results are discussed in terms of the role of contaminants in the observed synthesis, the "normalcy" of Acetabularia chloroplasts, the synthetic pathways for amino acids in plastids, and the implications of these observations for cell compartmentation and chloroplast autonomy.

scholarly journals SUN-266 Protein Induced Pancreatic Hormone Secretion Is Modulated by Vagal CaSR

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Mariana Norton ◽  
Simon C Cork ◽  
Aldara Martin Alonso ◽  
Anna G Roberts ◽  
Yateen S Patel ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Hormone Secretion ◽  
Sensory Information ◽  
Glucagon Secretion ◽  
Vagal Afferents ◽  
Acid Uptake

Abstract The existence of a vago-vagal entero-pancreatic pathway, where sensory information from the gut can signal via vagal afferents to the brain to mediate changes in pancreatic function, has been recognised for over a century, and investigated extensively with regards to pancreatic exocrine secretions. However, the role of such pathways in pancreatic endocrine secretions has received less attention. The secretion of insulin and glucagon in response to protein and amino acids is conserved across species. This effect is thought to promote amino acid uptake into tissues without concomitant hypoglycaemia. We found that the essential amino acid L-Phenylalanine potently stimulates glucagon secretion, even when administered directly into the gut at small doses unlikely to significantly raise systematic levels. Administration of L-Phenylalanine also increased neuronal activation in the rat and mouse dorsal vagal complex, the central nervous system region directly innervated by vagal afferents. L-Phenylalanine modulates the activity of the calcium sensing receptor (CaSR), a nutrient sensor more commonly known for its role in calcium homeostasis, but which is thought to also act as a sensor of aromatic amino acids. Interestingly, the CaSR is one of the few nutrient sensors expressed in vagal afferents and in vitro calcium imaging revealed CaSR synthetic agonists activate subpopulations of vagal afferents. The role of CaSR in vivo was investigated further by selectively knocking down the CaSR in vagal afferents. Briefly, CaSR floxed mice were bilaterally injected directly into the nodose ganglion, where the cell bodies of vagal afferents are located, with a cre expressing adeno-associated virus. CaSR knockdown did not interfere with normal food intake, nor the vagal-dependent anorectic effects of cholecystokinin, or of L-Phenylalanine. However, it did blunt protein-induced glucagon secretion, suggesting involvement of the CaSR in the vagus nerve in protein sensing and glucose homeostasis. Future studies are required to determine the importance of vagal CaSR in protein induced pancreatic endocrine secretions, and the possibility of exploiting this circuit to develop new anti-diabetic therapies.

Studies on Synergism between Glucose and Amino Acids with Respect to Insulin Release in vitro

1980 ◽  
Vol 35 (1-2) ◽  
pp. 72-75 ◽  
Author(s):  
Qamar Khalid ◽  
M. Ataur Rahman
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Insulin Release ◽  
Direct Effects ◽  
Isolated Rat Islets ◽  
Effect Of Glucose ◽  
Stimulate Insulin Release

Abstract The mutual enhancement of the effect of insulin release by glucose and amino acids is not clearly understood. Present in vitro studies with isolated rat islets were undertaken to elaborate the role of amino acids on insulin release, particularly their interaction with glucose as well as among each other, which has been reported to lead to synergism in the hum an subjects.In the presence of 8.3 mм glucose, both arginine, as well as, leucine potentiated the effect of glucose which increased progressively with the increasing concentrations of the amino acid. This effect of arginine was not synergistic in nature because arginine did not stimulate insulin release in the absence of glucose.The effect of glucose and leucine was found to be additive and not synergistic.No synergism was exhibited by any of the amino acid pairs tested in the present study. Thus both phenylalanine and lysine did not potentiate the effect of either arginine or leucine. Arginine showed a mild, but significant potentiating effect on leucine-stimulated insulin release.It is suggested that synergism between glucose and amino acids and between certain amino acid pairs reported in m an may not be due to the direct effects of these stimuli on the beta cells, but some other factors in vivo may be involved.

scholarly journals Filling Gaps in Bacterial Amino Acid Biosynthesis Pathways with High-throughput Genetics

2017 ◽  
Author(s):  
Morgan N. Price ◽  
Grant M. Zane ◽  
Jennifer V. Kuehl ◽  
Ryan A. Melnyk ◽  
Judy D. Wall ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
High Throughput ◽  
Heterotrophic Bacteria ◽  
Current Knowledge ◽  
Acid Synthesis ◽  
Amino Acid Biosynthesis ◽  
Desulfovibrio Vulgaris ◽  
Acid Biosynthesis ◽  
Amino Acid Synthesis

AbstractFor many bacteria with sequenced genomes, we do not understand how they synthesize some amino acids. This makes it challenging to reconstruct their metabolism, and has led to speculation that bacteria might be cross-feeding amino acids. We studied heterotrophic bacteria from 10 different genera that grow without added amino acids even though an automated tool predicts that the bacteria have gaps in their amino acid synthesis pathways. Across these bacteria, there were 11 gaps in their amino acid biosynthesis pathways that we could not fill using current knowledge. Using genome-wide mutant fitness data, we identified novel enzymes that fill 9 of the 11 gaps and hence explain the biosynthesis of methionine, threonine, serine, or histidine by bacteria from six genera. We also found that the sulfate-reducing bacteriumDesulfovibrio vulgarissynthesizes homocysteine (which is a precursor to methionine) by using DUF39, NIL/ferredoxin, and COG2122 proteins, and that homoserine is not an intermediate in this pathway. Our results suggest that most free-living bacteria can likely make all 20 amino acids and illustrate how high-throughput genetics can uncover previously-unknown amino acid biosynthesis genes.

scholarly journals Methylation of nuclear proteins by dimethylnitrosamine and by methionine in the rat in vivo

1971 ◽  
Vol 124 (4) ◽  
pp. 725-739 ◽  
Author(s):  
C. Turberville ◽  
V. M. Craddock
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rat Liver ◽  
Column Chromatography ◽  
Nuclear Proteins ◽  
Methyl Groups ◽  
Liver And Kidney ◽  
Methionine Residues

1. The incorporation of methyl groups into histones from dimethylnitrosamine and from methionine was studied by injection of the labelled compounds, isolation of rat liver and kidney histones, and analysis of hydrolysates by column chromatography. 2. Labelled methionine gave rise to labelled ∈-N-methyl-lysine, di-∈-N-methyl-lysine and an amino acid presumed to be ω-N-methyl-arginine. 3. Administration of labelled dimethylnitrosamine gave rise to labelled S-methylcysteine, 1-methylhistidine, 3-methylhistidine and ∈-N-methyl-lysine derived from the alkylating metabolite of dimethylnitrosamine. In addition, labelled formaldehyde released by metabolism of dimethylnitrosamine leads to the formation of labelled S-adenosylmethionine, and hence to labelling of ∈-N-methyl-lysine, di-∈-N-methyl-lysine and ω-N-methylarginine by enzymic methylation. 4. The formation of ∈-N-methyl-lysine by alkylation of liver histones was confirmed by using doubly labelled dimethylnitrosamine to discriminate between direct chemical alkylation and enzymic methylation via S-adenosylmethionine. These experiments also suggested the possibility that methionine residues in the histones were alkylated to give methylmethionine sulphonium residues. 5. The extent of alkylation of liver histones was maximal at about 5h after dosing and declined between 5 and 24h. The methylated amino acids resulting from direct chemical alkylation were preferentially lost: this is ascribed to necrosis of the more highly alkylated cells. 6. Liver histones were about four times as alkylated as kidney histones; the extent of alkylation of liver histones was similar to that of liver total nuclear proteins. 7. Methyl methanesulphonate (120mg/kg) alkylated liver histones to a greater extent than did dimethylnitrosamine. Diethylnitrosamine also alkylated liver histones. 8. The results are discussed with regard to the possible effects of alkylation on histone function, and the possible role of histone alkylation in carcinogenesis by the three compounds.

10 THE ROLE OF DIETARY L-SERINE IN THE REGULATION OF INTESTINAL MUCUS BARRIER DURING INFLAMMATION

2020 ◽  
Vol 26 (Supplement_1) ◽  
pp. S42-S42
Author(s):  
Kohei Sugihara ◽  
Nobuhiko Kamada
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Gut Microbiota ◽  
Control Diet ◽  
Bacterial Strains ◽  
Germ Free ◽  
Intestinal Mucus ◽  
Gnotobiotic Mice ◽  
Mucus Barrier

Abstract Background Recent accumulating evidence suggests that amino acids have crucial roles in the maintenance of intestinal homeostasis. In inflammatory bowel disease (IBD), amino acid metabolism is changed in both host and the gut microbiota. Among amino acids, L-serine plays a central role in several metabolic processes that are essential for the growth and survival of both mammalian and bacterial cells. However, the role of L-serine in intestinal homeostasis and IBD remains incompletely understood. In this study, we investigated the effect of dietary L-serine on intestinal inflammation in a murine model of colitis. Methods Specific pathogen-free (SPF) mice were fed either a control diet (amino acid-based diet) or an L-serine-deficient diet (SDD). Colitis was induced by the treatment of dextran sodium sulfate (DSS). The gut microbiome was analyzed by 16S rRNA sequencing. We also evaluate the effect of dietary L-serine in germ-free mice and gnotobiotic mice that were colonized by a consortium of non-mucolytic bacterial strains or the consortium plus mucolytic bacterial strains. Results We found that the SDD exacerbated experimental colitis in SPF mice. However, the severity of colitis in SDD-fed mice was comparable to control diet-fed mice in germ-free condition, suggesting that the gut microbiota is required for exacerbation of colitis caused by the restriction of dietary L-serine. The gut microbiome analysis revealed that dietary L-serine restriction fosters the blooms of a mucus-degrading bacterium Akkermansia muciniphila and adherent-invasive Escherichia coli in the inflamed gut. Consistent with the expansion of mucolytic bacteria, SDD-fed mice showed a loss of the intestinal mucus layer. Dysfunction of the mucus barrier resulted in increased intestinal permeability, thereby leading to bacterial translocation to the intestinal mucosa, which subsequently increased the severity of colitis. The increased intestinal permeability and subsequent bacterial translocation were observed in SDD-fed gnotobiotic mice that colonized by mucolytic bacteria. In contrast, dietary L-serine restriction did not alter intestinal barrier integrity in gnotobiotic mice that colonized only by non-mucolytic bacteria. Conclusion Our results suggest that dietary L-serine regulates the integrity of the intestinal mucus barrier during inflammation by limiting the expansion of mucus degrading bacteria.

scholarly journals Untargeted Metabolomics Uncovers the Essential Lysine Transporter in Toxoplasma gondii

Metabolites ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 476
Author(s):  
Joachim Kloehn ◽  
Matteo Lunghi ◽  
Emmanuel Varesio ◽  
David Dubois ◽  
Dominique Soldati-Favre
Keyword(s):  
Amino Acids ◽  
Toxoplasma Gondii ◽  
Rna Degradation ◽  
Major Facilitator Superfamily ◽  
Untargeted Metabolomics ◽  
Apicomplexan Parasites ◽  
Obligate Intracellular ◽  
Intracellular Parasites ◽  
Major Facilitator ◽  
Plasma Membrane Transporter

Apicomplexan parasites are responsible for devastating diseases, including malaria, toxoplasmosis, and cryptosporidiosis. Current treatments are limited by emerging resistance to, as well as the high cost and toxicity of existing drugs. As obligate intracellular parasites, apicomplexans rely on the uptake of many essential metabolites from their host. Toxoplasma gondii, the causative agent of toxoplasmosis, is auxotrophic for several metabolites, including sugars (e.g., myo-inositol), amino acids (e.g., tyrosine), lipidic compounds and lipid precursors (cholesterol, choline), vitamins, cofactors (thiamine) and others. To date, only few apicomplexan metabolite transporters have been characterized and assigned a substrate. Here, we set out to investigate whether untargeted metabolomics can be used to identify the substrate of an uncharacterized transporter. Based on existing genome- and proteome-wide datasets, we have identified an essential plasma membrane transporter of the major facilitator superfamily in T. gondii—previously termed TgApiAT6-1. Using an inducible system based on RNA degradation, TgApiAT6-1 was depleted, and the mutant parasite’s metabolome was compared to that of non-depleted parasites. The most significantly reduced metabolite in parasites depleted in TgApiAT6-1 was identified as the amino acid lysine, for which T. gondii is predicted to be auxotrophic. Using stable isotope-labeled amino acids, we confirmed that TgApiAT6-1 is required for efficient lysine uptake. Our findings highlight untargeted metabolomics as a powerful tool to identify the substrate of orphan transporters.

scholarly journals MetR-Regulated Vibrio cholerae Metabolism Is Required for Virulence

mBio ◽  
2012 ◽  
Vol 3 (5) ◽  
Author(s):  
Ryan W. Bogard ◽  
Bryan W. Davies ◽  
John J. Mekalanos
Keyword(s):  
Amino Acid ◽  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Current Knowledge ◽  
Intestinal Colonization ◽  
Wild Type ◽  
Pathogenic Potential ◽  
Content Type ◽  
Mouse Intestine

ABSTRACTLysR-type transcriptional regulators (LTTRs) are the largest, most diverse family of prokaryotic transcription factors, with regulatory roles spanning metabolism, cell growth and division, and pathogenesis. Using a sequence-defined transposon mutant library, we screened a panel ofV. choleraeEl Tor mutants to identify LTTRs required for host intestinal colonization. Surprisingly, out of 38 LTTRs, only one severely affected intestinal colonization in the suckling mouse model of cholera: the methionine metabolism regulator, MetR. Genetic analysis of genes influenced by MetR revealed thatglyA1andmetJwere also required for intestinal colonization. Chromatin immunoprecipitation of MetR and quantitative reverse transcription-PCR (qRT-PCR) confirmed interaction with and regulation ofglyA1, indicating that misregulation ofglyA1is likely responsible for the colonization defect observed in themetRmutant. TheglyA1mutant was auxotrophic for glycine but exhibited wild-type trimethoprim sensitivity, making folate deficiency an unlikely cause of its colonization defect. MetJ regulatory mutants are not auxotrophic but are likely altered in the regulation of amino acid-biosynthetic pathways, including those for methionine, glycine, and serine, and this misregulation likely explains its colonization defect. However, mutants defective in methionine, serine, and cysteine biosynthesis exhibited wild-type virulence, suggesting that these amino acids can be scavenged in vivo. Taken together, our results suggest that glycine biosynthesis may be required to alleviate an in vivo nutritional restriction in the mouse intestine; however, additional roles for glycine may exist. Irrespective of the precise nature of this requirement, this study illustrates the importance of pathogen metabolism, and the regulation thereof, as a virulence factor.IMPORTANCEVibrio choleraecontinues to be a severe cause of morbidity and mortality in developing countries. Identification ofV. choleraefactors critical to disease progression offers the potential to develop or improve upon therapeutics and prevention strategies. To increase the efficiency of virulence factor discovery, we employed a regulator-centric approach to multiplex our in vivo screening capabilities and allow whole regulons inV. choleraeto be interrogated for pathogenic potential. We identified MetR as a new virulence regulator and serine hydroxymethyltransferase GlyA1 as a new MetR-regulated virulence factor, both required byV. choleraeto colonize the infant mouse intestine. Bacterial metabolism is a prerequisite to virulence, and current knowledge of in vivo metabolism of pathogens is limited. Here, we expand the known role of amino acid metabolism and regulation in virulence and offer new insights into the in vivo metabolic requirements ofV. choleraewithin the mouse intestine.

scholarly journals Biological role of D-amino acid oxidase and D-aspartate oxidase. Effects of D-amino acids.

1993 ◽  
Vol 268 (36) ◽  
pp. 26941-26949
Author(s):  
A D'Aniello ◽  
G D'Onofrio ◽  
M Pischetola ◽  
G D'Aniello ◽  
A Vetere ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Biological Role ◽  
Acid Oxidase ◽  
Amino Acid Oxidase

scholarly journals Roles of the C-Terminal Amino Acids of Non-Hexameric Helicases: Insights from Escherichia coli UvrD

2021 ◽  
Vol 22 (3) ◽  
pp. 1018
Author(s):  
Hiroaki Yokota
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Amino Acid ◽  
Single Molecule ◽  
Underlying Mechanism ◽  
Amino Acid Sequences ◽  
E Coli ◽  
X Ray Crystallography ◽  
Terminal Amino

Helicases are nucleic acid-unwinding enzymes that are involved in the maintenance of genome integrity. Several parts of the amino acid sequences of helicases are very similar, and these quite well-conserved amino acid sequences are termed “helicase motifs”. Previous studies by X-ray crystallography and single-molecule measurements have suggested a common underlying mechanism for their function. These studies indicate the role of the helicase motifs in unwinding nucleic acids. In contrast, the sequence and length of the C-terminal amino acids of helicases are highly variable. In this paper, I review past and recent studies that proposed helicase mechanisms and studies that investigated the roles of the C-terminal amino acids on helicase and dimerization activities, primarily on the non-hexermeric Escherichia coli (E. coli) UvrD helicase. Then, I center on my recent study of single-molecule direct visualization of a UvrD mutant lacking the C-terminal 40 amino acids (UvrDΔ40C) used in studies proposing the monomer helicase model. The study demonstrated that multiple UvrDΔ40C molecules jointly participated in DNA unwinding, presumably by forming an oligomer. Thus, the single-molecule observation addressed how the C-terminal amino acids affect the number of helicases bound to DNA, oligomerization, and unwinding activity, which can be applied to other helicases.

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