Essential Aromatic Amino Acids Research Articles

A codon-based live-cell biomonitoring system for assessing intracellular phenylalanine bioavailability in cyanobacteria

Phenylalanine, as an essential aromatic amino acid, is not only needed for protein and vital molecules such as neurotransmitter and hormone synthesis but also a substrate for the biosynthesis of phenylpropanoids and various bioactive compounds. The metabolism of phenylalanine is dynamic and transitory, which would otherwise inhibit cell growth. Therefore, it is challenging and imperative to monitor intracellular phenylalanine bioavailability in real time, which has great significance for evaluating the effectiveness of introducing pathway-specific genetic modifications to enhance phenylalanine generation. In this study, we proposed a live-cell biomonitoring system to assess phenylalanine bioavailability in real time in cyanobacteria based on codon degeneracy and species-specific usage bias. The biomonitoring system was generated through genetic modification of phenylalanine codons in the chloramphenicol antibiotic resistance gene to wholly preferred and rare codons, in combination with an orthogonal constitutive promoter Trc to express these genes. Cyanobacterial cells equipped with a preferred codon-based gene showed a significant growth advantage over those with rare codons under antibiotic pressure, while the delayed growth caused by rare codon-based genes could be rescued by supplementing phenylalanine in the cultivation medium. Increasing intracellular phenylalanine bioavailability could promote rare codon-based gene containing cell growth to a similar level as wild-type strains harboring preferred codon-based gene, providing a live-cell visualized screening method to relatively define phenylalanine content from either random mutation libraries or pathway-specific engineering cyanobacterial chassis before conducting labor-intensive quantitative measurements.

Functional characterization of novel mutations in the conserved region of EPSPS for herbicide resistance in pigeonpea: structure-based coherent design

Prospectively, agroecosystems for the growth of crops provide the potential fertile, productive, and tropical environment which attracts infestation by weedy plant species that compete with the primary crop plants. Infestation by weed is a major biotic stress factor faced by pigeonpea that hampers the productivity of the crop. In the modern era with the development of chemicals the problem of weed infestation is dealt with armours called herbicides. The most widely utilized, post-emergent, broad-spectrum herbicide has an essential active ingredient called glyphosate. Glyphosate mechanistically inhibits a chloroplastic enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) by competitively interacting with the PEP binding site which hinders the shikimate pathway and the production of essential aromatic amino acids (Phe, Tyr, Trp) and other secondary metabolites in plants. Moreover, herbicide spray for weed management is lethal to both the primary crop and the weeds. Therefore, it is critical to develop herbicide-resistant crops for field purposes to reduce the associated yield and economic losses. In this study, the in-silico analysis drove the selection and validation of the point mutations in the conserved region of the EPSPS gene, which confers efficient herbicide resistance to mutated-CcEPSPS enzyme along with the retention of the normal enzyme function. An optimized in-silico validation of the target mutation before the development of the genome-edited resistant plant lines is a prerequisite for testing their efficacy as a proof of concept. We validated the combination of GATIPS mutation for its no-cost effect at the enzyme level via molecular dynamic (MD) simulation. Communicated by Ramaswamy H. Sarma

Microbial-Derived Tryptophan Metabolites and Their Role in Neurological Disease: Anthranilic Acid and Anthranilic Acid Derivatives.

The gut microbiome provides the host access to otherwise indigestible nutrients, which are often further metabolized by the microbiome into bioactive components. The gut microbiome can also shift the balance of host-produced compounds, which may alter host health. One precursor to bioactive metabolites is the essential aromatic amino acid tryptophan. Tryptophan is mostly shunted into the kynurenine pathway but is also the primary metabolite for serotonin production and the bacterial indole pathway. Balance between tryptophan-derived bioactive metabolites is crucial for neurological homeostasis and metabolic imbalance can trigger or exacerbate neurological diseases. Alzheimer's, depression, and schizophrenia have been linked to diverging levels of tryptophan-derived anthranilic, kynurenic, and quinolinic acid. Anthranilic acid from collective microbiome metabolism plays a complex but important role in systemic host health. Although anthranilic acid and its metabolic products are of great importance for host-microbe interaction in neurological health, literature examining the mechanistic relationships between microbial production, host regulation, and neurological diseases is scarce and at times conflicting. This narrative review provides an overview of the current understanding of anthranilic acid's role in neurological health and disease, with particular focus on the contribution of the gut microbiome, the gut-brain axis, and the involvement of the three major tryptophan pathways.

Profile and potential role of novel metabolite biomarkers, especially indoleacrylic acid, in pathogenesis of neuromyelitis optica spectrum disorders.

Background: Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune central nervous system (CNS) inflammatory and demyelinating disorder that can lead to serious disability and mortality. Humoral fluid biomarkers with specific, convenient, and efficient profiles that could characterize and monitor disease activity or severity are very useful. We aimed to develop a sensitive and high-throughput liquid chromatography-tandem mass spectrometry (LC-MS)/MS-based analytical method for novel biomarkers finding in NMOSD patients and verified its function tentatively. Methods: Serum samples were collected from 47 NMOSD patients, 18 patients with other neurological disorders (ONDs), and 35 healthy controls (HC). Cerebrospinal fluid (CSF) samples were collected from 18 NMOSD and 17 OND patients. Three aromatic amino acids (phenylalanine, tyrosine, and tryptophan) and nine important metabolites that included phenylacetylglutamine (PAGln), indoleacrylic acid (IA), 3-indole acetic acid (IAA), 5-hydroxyindoleacetic acid (HIAA), hippuric acid (HA), I-3-carboxylic acid (I-3-CA), kynurenine (KYN), kynurenic acid (KYNA), and quinine (QUIN) were analyzed by using the liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method. The profile of IA was further analyzed, and its function was verified in an astrocyte injury model stimulated by NMO-IgG, which represents important events in NMOSD pathogenesis. Results: In the serum, tyrosine and some of the tryptophan metabolites IA and I-3-CA decreased, and HIAA increased significantly in NMOSD patients. The CSF levels of phenylalanine and tyrosine showed a significant increase exactly during the relapse stage, and IA in the CSF was also increased markedly during the relapse and remission phases. All conversion ratios had similar profiles with their level fluctuations. In addition, the serum IA levels negatively correlated with glial fibrillary acidic protein (GFAP), and neurofilament light (NfL) levels in the serum of NMOSD patients were measured by using ultra-sensitive single-molecule arrays (Simoa). IA showed an anti-inflammatory effect in an in vitro astrocyte injury model. Conclusion: Our data suggest that essential aromatic amino acid tryptophan metabolites IA in the serum or CSF may serve as a novel promising biomarker to monitor and predict the activity and severity of NMOSD disease. Supplying or enhancing IA function can promote anti-inflammatory responses and may have therapeutic benefits.

Bioorthogonal Chemical Imaging of Cell Metabolism Regulated by Aromatic Amino Acids.

Essential aromatic amino acids (AAAs) are building blocks for synthesizing new biomasses in cells and sustaining normal biological functions. For example, an abundant supply of AAAs is important for cancer cells to maintain their rapid growth and division. With this, there is a rising demand for a highly specific, noninvasive imaging approach with minimal sample preparation to directly visualize how cells harness AAAs for their metabolism in situ. Here, we develop an optical imaging platform that combines deuterium oxide (D2O) probing with stimulated Raman scattering (DO-SRS) and integrates DO-SRS with two-photon excitation fluorescence (2PEF) into a single microscope to directly visualize the metabolic activities of HeLa cells under AAA regulation. Collectively, the DO-SRS platform provides high spatial resolution and specificity of newly synthesized proteins and lipids in single HeLa cell units. In addition, the 2PEF modality can detect autofluorescence signals of nicotinamide adenine dinucleotide (NADH) and Flavin in a label-free manner. The imaging system described here is compatible with both in vitro and in vivo models, which is flexible for various experiments. The general workflow of this protocol includes cell culture, culture media preparation, cell synchronization, cell fixation, and sample imaging with DO-SRS and 2PEF modalities.

Intestinal permeability and its role in the pathogenesis and progress of non-alcoholic fatty liver disease. Review

Non‑alcoholic fatty liver disease (NAFLD) is a topical problem for the medicine worldwide, and its association with an «unhealthy» lifestyle and metabolic disorders is well established. The important role of dysbiosis of the intestinal microbiota in the NAFLD pathogenesis and the functioning of the intestine‑liver axis is emphasized. Data on the structure and functioning of the intestinal barrier in physiological conditions are presented. It has been proven that the presence of dysbiotic changes in the microbiota plays an important role in the disruption of the barrier function of the gastrointestinal tract, which in turn increases the level of physiological translocation of both bacteria and their toxins and their life products. Part of these harmful products comes to the liver through the portal vein (endotoxinemia). The antigens’ overload contributes to the development and progression of NAFLD (up to liver cirrhosis). The intestinal barrier is emphasized to be dynamic and sensitive to changes occurring in the intestine. The increased intestinal permeability and bacterial overgrowth syndrome (which is a source of increased endotoxemia) is observed in patients with NAFLD more frequently than in healthy subjects. Number of studies have revealed that the degree of intestinal permeability in NAFLD patients correlated with the steatosis severity. The factors that most significantly affect intestinal permeability in patients with NAFLD include microbial environment, bile acids, levels of fecal short‑chain fatty acids (mainly butyrate), the metabolism of the essential aromatic amino acid tryptophan, as well as the nature of nutrition, alcohol intake, medicinal preparations, stress, and level of physical activity, which act either directly or through the induction of intestinal microbiota dysbacteriosis. The increased intestinal permeability and its consequence — bacterial translocation, are noticed to be involved in the development of such complications as spontaneous bacterial peritonitis, hepatorenal syndrome, portal vein thrombosis, hepatic encephalopathy, hepatocellular carcinoma.

A comparative study revealed hyperspectral imaging as a potential standardized tool for the analysis of cuticle tanning over insect development

Cereal-feeding beetles are a major risk for cereal crop maintenance. Cereal weevils such as Sitophilus oryzae have symbiotic intracellular bacteria that provide essential aromatic amino acid to the host for the biosynthesis of their cuticle building blocks. Their cuticle is an important protective barrier against biotic and abiotic stresses, providing high resistance from insecticides. Quantitative optical methods specialized in insect cuticle analysis exist, but their scope of use and the repeatability of the results remain limited. Here, we investigated the potential of Hyperspectral Imaging (HSI) as a standardized cuticle analysis tool. Based on HSI, we acquired time series of average reflectance profiles from 400 to 1000 nm from symbiotic (with bacteria) and aposymbiotic (without bacteria) cereal weevils S. oryzae exposed to different nutritional stresses. We assessed the phenotypic changes of weevils under different diets throughout their development and demonstrated the agreement of the results between the HSI method and the classically used Red-Green-Blue analysis. Then, we compared the use of both technologies in laboratory conditions and highlighted the assets of HSI to develop a simple, automated, and standardized analysis tool. This is the first study showing the reliability and feasibility of HSI for a standardized analysis of insect cuticle changes.

The Role of Gut Microbiota-derived Tryptophan Metabolites in Mycobacterium tuberculosis Infection: A Mini-Review

The gut microbiota has a major contribution in human physiology and influences disease pathogenesis, including in tuberculosis (TB) lung infection. Gut-lung axis has demonstrated the interplay of these two organs, mediated by metabolites produced by the gut microbes or derived from host molecules transformation. Tryptophan (Trp) is one of the essential aromatic amino acids catabolized as kynurenine, serotonin (5-hydroxytryptamine), and indole derivatives, including indole propionic acid (IPA), via 3 pathways. The latter was microbiota-derived Trp catabolism, which has known to have an immunomodulatory role, as ligands for Aryl hydrocarbon Receptor (AhR). Intriguingly, Mycobacterium tuberculosis required Trp as a nitrogen source, especially in CD4+ T cells-generated stress, to survive in the phagosome of macrophage and to cause disease. Recently, IPA is identified as a new anti-mycobacterial compound, which is specific and has broad spectrum of anti-mycobacterial activity. The structural similarity of this gut microbiota-derived metabolite and Trp allows IPA to inhibit the TrpE anthranilate synthase in Trp biosynthesis pathway in Mtb. In this review, we summarize findings from recent work by focusing on the role of Trp metabolites in host cells in TB infection. A better understanding of this chemical signal could potentially serve as a novel strategy for managing this chronic inflammatory disease.

Post-Harvest LED Light Irradiation Affects Firmness, Bioactive Substances, and Amino Acid Compositions in Chili Pepper (Capsicum annum L.).

Chili pepper is an important vegetable and spice crop with high post-harvest deteriorations in terms of commercial and nutritional quality. Light-emitting diodes (LEDs) are eco-friendly light sources with various light spectra that have been demonstrated to improve the shelf-life of various vegetables by manipulating light quality; however, little is known about their effects on the post-harvest nutritional quality of chili peppers. This study investigated the effects of different LED lightings on the post-harvest firmness and nutritional quality of chili peppers. We found that red and blue light could increase the content of capsaicinoids, whereas white and red light could increase the essential and aromatic amino acid (AA) content in pepper. Nonetheless, the influence of light treatments on AA contents and compositions depends strongly on the pepper genotype, which was reflected by total AA content, single AA content, essential AA ratio, delicious AA ratio, etc., that change under different light treatments. Additionally, light affected fruit firmness and the content of nutrients such as chlorophyll, vitamin C, and total carotenoids, to varying degrees, depending on pepper genotypes. Thus, our findings indicate that LED-light irradiation is an efficient and promising strategy for preserving or improving the post-harvest commercial and nutritional quality of pepper fruit.

Probiotic potentials of the silkworm gut symbiont Enterococcus casseliflavusECB140, a promising L-tryptophan producer living inside the host.

L-tryptophan is an essential aromatic amino acid for the growth and development of animals. Studies about enteric L-tryptophan-producing bacteria are scarce. In this report, we characterized the probiotic potential of Enterococcus casseliflavus ECB140, focusing on its L-tryptophan production abilities. ECB140 strain was isolated from the silkworm gut and can survive under strong alkaline environmental conditions. Bacterial colonization traits (motility and biofilm) were examined and showed that only ECB140 produced flagellum and strong biofilms compared with other Enterococcus strains. Comparative genome sequence analyses showed that only ECB140 possessed a complete route for L-tryptophan synthesis among all 15 strains. High-performance liquid chromatography and qRT-PCR confirmed the capability of ECB140 to produce L-tryptophan. Besides, the genome also contains the biosynthesis pathways of several other essential amino acids, such as phenylalanine, threonine, valine, leucine, isoleucine and lysine. These results indicate that ECB140 has the ability to survive passage through the gut and could act as a candidate probiotic. The study describes a novel, natural silkworm gut symbiont capable of producing L-tryptophan. Enterococcus casseliflavus ECB140 physical and genomic attributes offer possibilities for its colonization and provide L-tryptophan for lepidopteran insects.

Chiral fluorescent sensor based on H8-BINOL for the high enantioselective recognition of d- and l-phenylalanine.

Phenylalanine an essential aromatic amino acid for humans and animals, cannot be synthesized by humans and animals on their own. However, it synthesizes important neurotransmitters and hormones in the body and is involved in gluconeogenesis and lipid metabolism. Moreover, the two opposite configurations of phenylalanine have different activities. For example, l-phenylalanine is a biologically active optical isomer involved in crucial biological processes, the lack of which will lead to intellectual disability, while d-phenylalanine only acts as a chiral intermediate. In this research, an H8-BINOL chiral fluorescent sensor modified with 1,2,3-triazole was synthesized in high yield (95%) by nucleophilic substitution and click reaction. The chiral fluorescent sensor showed high enantioselectivity toward phenylalanine. l-Phenylalanine enhanced the fluorescence response of the probe significantly, while d-phenylalanine had no obvious fluorescence response change. The enantioselective fluorescence enhancement ratio [ef = (IL − I0)/(ID − I0), where I0 is the fluorescence of the sensor without amino acids] for the highest fluorescence intensity at 20.0 equivalents of amino acids was 104.48. In this way, the probe could be used to identify and differentiate different configurations of phenylalanine.

Enhancing tryptophan production by balancing precursors in Escherichia coli.

Tryptophan, an essential aromatic amino acid, is widely used in animal feed, food additives, and pharmaceuticals. Although sustainable and environmentally friendly, microbial tryptophan production from renewable feedstocks is limited by low biosynthesis and transport rates. Here, an Escherichia coli strain capable of efficient tryptophan production was generated by improving and balancing the supply of precursors and by engineering membrane transporters. Tryptophan biosynthesis was increased by eliminating negative regulatory factors, blocking competing pathways, and preventing tryptophan degradation. Promoter engineering balanced the supply of the precursors erythrose-4-phosphate and phosphoenolpyruvate, as well as the availability of serine. Finally, the engineering of tryptophan transporters prevented feedback inhibition and growth toxicity. Fed-batch fermentation of the final strain (TRP12) in a 5 L bioreactor produced 52.1 g·L-1 of tryptophan, with a yield of 0.171 g·g-1 glucose and productivity of 1.45 g·L-1 ·h-1 . The metabolic engineering strategy described here paves the way for high-performance microbial cell factories aimed at the production of tryptophan as well as other valuable chemicals.

Trace elements and plasma metabolomics in a general population from Spain: The Hortega Study

BACKGROUND AND AIM: Limited studies have evaluated the joint influence of trace elements on metabolic pathways. We analyzed the association of 12 trace elements with 54 plasma metabolites in 1144 participants from the Hortega Study, a population-based sample from Spain. METHODS: Urine antimony (Sb), arsenic (As), As adjusted by arsenobetaine (Asb), barium (Ba), cadmium (Cd), chromium (Cr), cobalt (Co), molybdenum (Mo) and vanadium (V); and plasma copper (Cu), selenium (Se) and zinc (Zn) were measured with ICP-MS and AAS, respectively. Serum metabolomic profiles, including lipoprotein subclasses, were assessed by NMR-spectrometry. We jointly correlated metabolites by principal component (PC) analysis. Bayesian Kernel Machine Regression (BKMR) allowed to evaluate the influence of trace element mixtures on metabolomic profiles. RESULTS:The geometric means of trace element exposure biomarker levels were, 0.07, 68.69, 6.53, 62.03, 0.37, 3.55, 0.25, 26.09 and 2.08 μg/g for urine Sb, As, As adjusted by Asb, Ba, Cd, Cr, Co, Mo and V, and 93.88, 83.73 and 77.13 μg/L, for plasma Cu, Se and Zn. Cu was inversely associated with metabolic principal component (mPC) 1 (reflecting increasing non-essential and essential branch-chained aminoacids and bacterial co-metabolism versus decreasing VLDL lipoproteins subclasses); Se and Zn were inversely associated with mPC 2 (reflecting increasing essential aromatic aminoacids and bacterial co-metabolism); The corresponding associations for mPC 3 (reflecting increasing LDL lipoprotein subclasses) were positive for plasma Cu, Se and Zn and inverse for urine Co. Plasma Zn was inversely associated with mPC 4 (reflecting increasing HDL lipoprotein subclasses). These associations remained after multiple-trace element adjustment. BKMR to assess joint trace element exposure was confirmatory. CONCLUSIONS:Excessive exposure to Co, Cu, Se, and Zn was associated with metabolite profiles traditionally linked to cardiometabolic risk and bacterial co-metabolism. While our findings should be confirmed in other studies, interventions to prevent uncontrolled exposure to these trace elements may be needed. KEYWORDS: Microbiome, Mixtures, Metabolomics, Biomarkers of exposure

Adaptation of bacteria to glyphosate: a microevolutionary perspective of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase.

Glyphosate is the leading herbicide worldwide, but it also affects prokaryotes because it targets the central enzyme (5-enolpyruvylshikimate-3-phosphate, EPSP) of the shikimate pathway in the synthesis of the three essential aromatic amino acids in bacteria, fungi and plants. Our results reveal that bacteria may easily become resistant to glyphosate through changes in the 5-enolpyruvylshikimate-3-phosphate synthase active site. This indicates the importance of examining how glyphosate affects microbe-mediated ecosystem functions and human microbiomes.

Classification of the glyphosate target enzyme (5-enolpyruvylshikimate-3-phosphate synthase) for assessing sensitivity of organisms to the herbicide

Glyphosate is the most common broad-spectrum herbicide. It targets the key enzyme of the shikimate pathway, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which synthesizes three essential aromatic amino acids (phenylalanine, tyrosine and tryptophan) in plants. Because the shikimate pathway is also found in many prokaryotes and fungi, the widespread use of glyphosate may have unsuspected impacts on the diversity and composition of microbial communities, including the human gut microbiome. Here, we introduce the first bioinformatics method to assess the potential sensitivity of organisms to glyphosate based on the type of EPSPS enzyme. We have precomputed a dataset of EPSPS sequences from thousands of species that will be an invaluable resource to advancing the research field. This novel methodology can classify sequences from nearly 90% of eukaryotes and >80% of prokaryotes. A conservative estimate from our results shows that 54% of species in the core human gut microbiome are sensitive to glyphosate.

Gut microbiota-derived tryptophan metabolism mediates renal fibrosis by aryl hydrocarbon receptor signaling activation.

The gut microbiota has a crucial effect on regulating the intestinal mucosal immunity and maintaining intestinal homeostasis both in health and in disease state. Many effects are mediated by gut microbiota-derived metabolites and tryptophan, an essential aromatic amino acid, is considered important among many metabolites in the crosstalk between gut microbiota and the host. Kynurenine, serotonin, and indole derivatives are derived from the three major tryptophan metabolism pathways modulated by gut microbiota directly or indirectly. Aryl hydrocarbon receptor (AHR) is a cytoplasmic ligand-activated transcription factor involved in multiple cellular processes. Tryptophan metabolites as ligands can activate AHR signaling in various diseases such as inflammation, oxidative stress injury, cancer, aging-related diseases, cardiovascular diseases (CVD), and chronic kidney diseases (CKD). Accumulated uremic toxins in the body fluids of CKD patients activate AHR and affect disease progression. In this review, we will elucidate the relationship between gut microbiota-derived uremic toxins by tryptophan metabolism and AHR activation in CKD and its complications. This review will provide therapeutic avenues for targeting CKD and concurrently present challenges and opportunities for designing new therapeutic strategies against renal fibrosis.

Metabolic Engineering and Fermentation Process Strategies for L-Tryptophan Production by Escherichia coli

L-tryptophan is an essential aromatic amino acid that has been widely used in medicine, food, and animal feed. Microbial biosynthesis of L-tryptophan through metabolic engineering approaches represents a sustainable, cost-effective, and environmentally friendly route compared to chemical synthesis. In particular, metabolic pathway engineering allows enhanced product titers by inactivating/blocking the competing pathways, increasing the intracellular level of essential precursors, and overexpressing rate-limiting enzymatic steps. Based on the route of the L-tryptophan biosynthesis pathway, this review presents a systematic and detailed summary of the contemporary metabolic engineering approaches employed for L-tryptophan production. In addition to the engineering of the L-tryptophan biosynthesis pathway, the metabolic engineering modification of carbon source uptake, by-product formation, key regulatory factors, and the polyhydroxybutyrate biosynthesis pathway in L-tryptophan biosynthesis are discussed. Moreover, fermentation bioprocess optimization strategies used for L-tryptophan overproduction are also delineated. Towards the end, the review is wrapped up with the concluding remarks, and future strategies are outlined for the development of a high L-tryptophan production strain.

Imbalance of tyrosine by modulating TyrA arogenate dehydrogenases impacts growth and development of Arabidopsis thaliana.

l-Tyrosine is an essential aromatic amino acid required for the synthesis of proteins and a diverse array of plant natural products; however, little is known on how the levels of tyrosine are controlled in planta and linked to overall growth and development. Most plants synthesize tyrosine by TyrA arogenate dehydrogenases, which are strongly feedback-inhibited by tyrosine and encoded by TyrA1 and TyrA2 genes in Arabidopsis thaliana. While TyrA enzymes have been extensively characterized at biochemical levels, their in planta functions remain uncertain. Here we found that TyrA1 suppression reduces seed yield due to impaired anther dehiscence, whereas TyrA2 knockout leads to slow growth with reticulate leaves. The tyra2 mutant phenotypes were exacerbated by TyrA1 suppression and rescued by the expression of TyrA2, TyrA1 or tyrosine feeding. Low-light conditions synchronized the tyra2 and wild-type growth, and ameliorated the tyra2 leaf reticulation. After shifting to normal light, tyra2 transiently decreased tyrosine and subsequently increased aspartate before the appearance of the leaf phenotypes. Overexpression of the deregulated TyrA enzymes led to hyper-accumulation of tyrosine, which was also accompanied by elevated aspartate and reticulate leaves. These results revealed that TyrA1 and TyrA2 have distinct and overlapping functions in flower and leaf development, respectively, and that imbalance of tyrosine, caused by altered TyrA activity and regulation, impacts growth and development of Arabidopsis. The findings provide critical bases for improving the production of tyrosine and its derived natural products, and further elucidating the coordinated metabolic and physiological processes to maintain tyrosine levels in plants.

The aromatic amino acid sensor GPR142 controls metabolism through balanced regulation of pancreatic and gut hormones

ObjectivesGPR142, which is highly expressed in pancreatic islets, has recently been deorphanized as a receptor for aromatic amino acids; however, its physiological role and pharmacological potential is unclear. Methods and resultsWe find that GPR142 is expressed not only in β- but also in α-cells of the islets as well as in enteroendocrine cells, and we confirm that GPR142 is a highly selective sensor of essential aromatic amino acids, in particular Trp and oligopeptides with N-terminal Trp. GPR142 knock-out mice displayed a very limited metabolic phenotype but demonstrated that L-Trp induced secretion of pancreatic and gut hormones is mediated through GPR142 but that the receptor is not required for protein-induced hormone secretion. A synthetic GPR142 agonist stimulated insulin and glucagon as well as GIP, CCK, and GLP-1 secretion. In particular, GIP secretion was sensitive to oral administration of the GPR142 agonist an effect which in contrast to the other hormones was blocked by protein load. Oral administration of the GPR142 agonist increased [3H]-2-deoxyglucose uptake in muscle and fat depots mediated through insulin action while it lowered liver glycogen conceivably mediated through glucagon, and, consequently, it did not lower total blood glucose. Nevertheless, acute administration of the GPR142 agonist strongly improved oral glucose tolerance in both lean and obese mice as well as Zucker fatty rat. Six weeks in-feed chronic treatment with the GPR142 agonist did not affect body weight in DIO mice, but increased energy expenditure and carbohydrate utilization, lowered basal glucose, and improved insulin sensitivity. ConclusionsGPR142 functions as a sensor of aromatic amino acids, controlling GIP but also CCK and GLP-1 as well as insulin and glucagon in the pancreas. GPR142 agonists could have novel interesting potential in modifying metabolism through a balanced action of gut hormones as well as both insulin and glucagon.

Ceftriaxone and Phenylalanine Combination as Broad Spectrum Antimicrobials Therapy

Background: Ceftriaxone belongs to the third-generation β-lactam antibiotics and it is useful for the treatment of a number of infectious diseases caused by both aerobic and anaerobic Gram-positive and Gram-negative bacteria. Phenylalanine is an essential aromatic amino acid of human being, from which dopamine and norepinephrine neurotransmitters are being synthesized. In the present study, we examined their combined efficacy against different types of pathogenic bacterial strains. Objective: The aim of the study was designed to investigate the effects of ceftriaxone combination with phenylalanine on antimicrobial activity Method: Gram positive-bacteria and Gram negative- including Klebsiella pneumoniae, – ATCC 25923, Proteus vulgaris, Escherichia coli, Serratia marcrescens, Staphylococcus epidermis, Alpha haemolyticus streptococcus, Enterococcus faecium, Pseudomonas aeruginosa, Listeria monocytogenes ATCC 7644, Enterococcus durans, Salmonella kentucky, Enterobacter aerogenes ATCC 13048 and Candida albicans ATCC 26555 were exposed to ceftriaxone and phenylalanine based on disk-diffusion method, and Minimum inhibition concentration (MIC) was determined with ceftriaxone. Results: 0.3 mol/L ceftriaxone and 0.3 mol/L phenylalanine solutions were mixed and observed greater zone of inhibition than ceftriaxone or phenylalanine alone against above mentioned bacterial strains. These results might open up a new avenue for using phenylalanine in combination with ceftriaxone to lower MIC level for better antibacterial effect, to reduce side effects of antibiotics, and to reduce emerging threats of antibiotic resistance bacteria. Conclusion: In this study, combined use of phenylalanine and ceftriaxone has revealed increased antimicrobial sensitivity against some selected both Gram positive and Gram negative bacteria in vitro. Keywords: Ceftriaxone, phenylalanine, pathogenic bacteria strains, antimicrobial activity, beta-lactam antibiotics, bacterial strains.