l-arginine is a versatile amino acid with a number of bioactive metabolites. Increasing evidence implicates altered arginine metabolism in the aging and neurodegenerative processes. The present study, for the first time, determined the effects of sex and estrous cycle on the brain and blood (plasma) arginine metabolic profile in naïve rats. Female rats displayed significantly lower levels of l-arginine in the frontal cortex and three sub-regions of the hippocampus when compared to male rats. Moreover, female rats had significantly higher levels of l-arginine and γ-aminobutyric acid, but lower levels of l-ornithine, agmatine and putrescine, in plasma relative to male rats. The observed sex difference in brain l-arginine appeared to be independent of the enzymes involved in its metabolism, de novo synthesis and blood-to-brain transport (cationic acid transporter 1 protein expression at least), as well as circulating l-arginine. While the estrous cycle did not affect l-arginine and its metabolites in the brain, there were estrous cycle phase-dependent changes in plasma l-arginine. These findings demonstrate the sex difference in brain l-arginine in the estrous cycle-independent manner. Since peripheral blood has been increasingly used to identify biomarkers of brain pathology, the influences of sex and estrous cycle on blood arginine metabolic profile need attention when experimental research involves female rodents.
相似文献In our previous study, one-step pyruvate and d-alanine production from d,l-alanine by a whole-cell biocatalyst Escherichia coli expressing l-amino acid deaminase (Pm1) derived from Proteus mirabilis was investigated. However, due to the low catalytic efficiency of Pm1, the pyruvate titer was relatively low. Here, semi-rational design based on site-directed saturation mutagenesis was carried out to improve the catalytic efficiency of Pm1. A novel high-throughput screening (HTS) method for pyruvate based on 2,4-dinitrophenylhydrazine indicator was then established. The catalytic efficiency (kcat/Km) of the mutant V437I screened out by this method was 1.88 times higher than wild type. Next, to improve the growth of the engineered strain BLK07, the genes encoding for Xpk and Fbp were integrated into its genome to construct non-oxidative glycolysis (NOG) pathway. Finally, the CRISPR/Cas9 system was used to integrate the N6-pm1-V437I gene into the genome of BLK07. Pyruvic acid titer of the plasmid-free strain reached 42.20 g/L with an l-alanine conversion rate of 77.62% and a d-alanine resolution of 82.4%. This work would accelerate the industrial production of pyruvate and d-alanine by biocatalysis, and the HTS method established here could be used to screen other Pm1 mutants with high pyruvate titers.
相似文献Oral mucositis is an inflammation of the oral mucosa mainly resulting from the cytotoxic effect of 5-fluorouracil (5-FU). The literature shows anti-inflammatory action of l-cysteine (l-cys) involving hydrogen sulfide (H2S). In view of these properties, we investigate the effect of l-cys in oral mucositis induced by 5-FU in hamsters. The animals were divided into the following groups: saline 0.9%, mechanical trauma, 5-FU 60–40 mg/kg, l-cys 10/40 mg and NaHS 27 µg/kg. 5-FU was administered on days 1st to 2nd; 4th day excoriations were made on the mucosa; 5th–6th received l-cys and NaHS. For data analysis, histological analyses, mast cell count, inflammatory and antioxidants markers, and immunohistochemistry (cyclooxygenase-2(COX-2)/inducible nitric oxide synthase (iNOs)/H2S) were performed. Results showed that l-cys decreased levels of inflammatory markers, mast cells, levels of COX-2, iNOS and increased levels of antioxidants markers and H2S when compared to the group 5-FU (p < 0.005). It is suggested that l-cys increases the H2S production with anti-inflammatory action in the 5-FU lesion.
相似文献l-Carnosine is an amino acid that acts as an anti-oxidant, anti-toxic and neuroprotective agent. There is a paucity of data about the effectiveness of l-Carnosine in the management of autism spectrum disorder (ASD) in children. This study aimed at investigating the effectiveness of l-Carnosine as adjunctive therapy in the management of ASD. This was a randomized controlled trial. Children aged 3–6 years with a diagnosis of mild to moderate ASD were assigned to standard care arm (occupational and speech therapy) and intervention care arm (l-Carnosine, 10–15 mg/kg in 2 divided doses) plus standard care treatment. The children were assessed at the baseline and the end of 2 months for the scores of Childhood Autism Rating Scale, Second Edition—Standard Version (CARS2-ST), Autism Treatment Evaluation Checklist (ATEC), BEARS sleep screening tool and 6-item Gastrointestinal Severity Index (6-GSI). Of the sixty-seven children enrolled, sixty-three children had completed the study. No statistically significant difference (p > 0.05) was observed for any of the outcome measures assessed. Supplementation of l-Carnosine did not improve the total score of CARS2-ST, ATEC, BEARS sleep screening tool and 6-GSI scores of children with ASD. Further investigations are needed with more objective assessments to critically validate the effectiveness of l-Carnosine on ASD children for more decisive results.
相似文献In this work, we prepared gold nanoparticles (AuNPs) by employing gluconic acid (GlcA) as reducing-cum-stabilizing agent. The proposed GlcA-AuNPs successfully worked as a colorimetric sensor for visual chiral recognition of aromatic amino acid enantiomers, namely tyrosine (d/l-Tyr), phenylalanine (d/l-Phe), and tryptophan (d/l-Trp). After adding L-types to GlcA-AuNPs solution, the color of the mixture changed from red to purple (or gray), while no obvious color change occurred on the addition of D-types. The effect can be detected by naked eyes. The particles have been characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy, zeta potential, the dynamic light scattering analysis as well as UV–Vis spectroscopy. This assay can be used to determine the enantiomeric excess of l-Trp in the range from 0 to + 100%. The method has advantages in simplicity, sensitivity, fast response, and low cost.
相似文献We succeeded in expressing selenocysteine β-lyase (SCL) from a lactic acid bacterium, Leuconostoc mesenteroides LK-151 (Lm-SCL), in the soluble fractions of Escherichia coli Rosetta (DE3) using a novel expression vector of pET21malb constructed by ourselves that has both maltose binding protein (MBP)- and 6?×?His-tag. Lm-SCL acted on l-selenocysteine, l-cysteine, and l-cysteine sulfinic acid but showed a high preference for l-selenocysteine. The kcat and kcat/Km values of Lm-SCL were determined to be 108 (min?1) and 42.0 (min?1?mM?1), respectively, and this was enough catalytic efficiency to suggest that Lm-SCL might also be involved in supplying elemental selenium from l-selenocysteine to selenoproteins like other SCLs. The optimum temperature and optimum pH of Lm-SCL were determined to be 37 °C and pH 6.5, respectively. Lm-SCL was stable at 37–45 °C and pH 6.5–7.5. Lm-SCL was completely inhibited by the addition of hydroxylamine, semicarbazide, and iodoacetic acid. The enzyme activity of Lm-SCL was decreased in the presence of various metal ions, especially Cu2+. The quaternary structure of Lm-SCL is a homodimer with a subunit molecular mass of 47.5 kDa. The similarity of the primary structure of Lm-SCL to other SCLs from Citrobacter freundii, Escherichia coli, humans, or mouse was calculated to be 47.0, 48.0, 12.5, or 24.0%, respectively. Unlike Ec-SCL, our mutational and molecular docking simulation studies revealed that C362 of Lm-SCL might also catalyze the deselenation of l-selenocysteine in addition to the desulfuration of l-cysteine.
相似文献To solve the bottleneck of plasmid instability during microbial fermentation of l-DOPA with recombinant Escherichia coli expressing heterologous tyrosine phenol lyase.
ResultsThe tyrosine phenol lyase from Fusobacterium nucleatum was constitutively expressed in E. coli and a fed-batch fermentation process with temperature down-shift cultivation was performed. Efficient strategies including replacing the original ampicillin resistance gene, as well as inserting cer site that is active for resolving plasmid multimers were applied. As a result, the plasmid stability was increased. The co-use of cer site on plasmid and kanamycin in culture medium resulted in proportion of plasmid containing cells maintained at 100% after fermentation for 35 h. The specific activity of tyrosine phenol lyase reached 1493 U/g dcw, while the volumetric activity increased from 2943 to 14,408 U/L for l-DOPA biosynthesis.
ConclusionsThe established strategies for plasmid stability is not only promoted the applicability of the recombinant cells for l-DOPA production, but also provides important guidance for industrial fermentation with improved microbial productivity.
相似文献At present, physicochemical properties of amino acid molecular crystals are of the utmost interest. The compounds where molecules have different chirality are the focus of particular interest. This paper, presents a study on the structural and electronic properties of crystalline l- and dl-valine within the framework of density functional theory including van der Waals interactions. The results of this study showed that electronic properties of the two forms of valine are similar at zero pressure. Pressure leads to different responses in these crystals which is manifested as various deformations of molecules. The pressure effect on the infrared spectra and distribution of electron density of l- and dl-valine has been studied.
相似文献Heptoses are important structural components of Gram-negative bacterium cell wall and participate in bacterial colonization, infection, and immune recognition. Current knowledge of NDP-heptose originating from d-sedoheptulose 7-phosphate in Grampositive bacterium remains limited. Here, in silico analysis suggested that the special tridomain NDP-heptose synthetases with isomerase, kinase, and nucleotidyltransferase activities are conservatively distributed in Actinobacteria class of Gram-positive bacterium. Enzymatical characterization of the tridomain proteins from different strains showed that they are involved in ADP-d-glycero-β-d-manno-heptose biosynthesis despite the unexpected discovery of kinase activities deficient in some proteins. The presence of three types of NDP-heptose synthetases in Gram-positive bacterium suggests that it is also a rich source of heptoses and the heptose moieties may play important roles in vivo. Our work updates the understanding of NDP-heptose biosynthesis in Gram-positive bacterium and lays a solid foundation for further physiological function explorations.
相似文献L-tryptophan has been used as a feed additive for swine and poultry and as a nutrient supplement for humans. However, some impurities in l-tryptophan have been reported as causative components of eosinophilia-myalgia syndrome. Therefore, from a safety perspective, it is important to analyze meat samples for these impurities. This study aims to develop an analytical method for the simultaneous detection of l-tryptophan impurities in meat products using LC–MS/MS. Among the various impurities, detection methods for (S)-2-amino-3-(5-hydroxy-1H-indol-3-yl)propanoic acid (5-hydroxytryptophan) (HTP), 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCA), 3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrrolo-[2,3-b]-indole-2-carboxylic acid (PIC), and 1,1′-ethylidenebistryptophan (EBT) and 2-(3-indoylmethyl)-l-tryptophan (IMT) were developed. The developed method allowed simultaneous determination of these four impurities in 5 min. No interferences from the matrix were observed, and the method showed good sensitivity to each analyte. The method detection limit and limit of quantification in meat matrices were below 11.2 and 35.7 μg/kg, respectively.
相似文献Pectinaceous agricultural residues rich in d-galacturonic acid (d-GalA), such as sugar beet pulp, are considered as promising feedstocks for waste-to-value conversions. Aspergillus niger is known for its strong pectinolytic activity. However, while specialized strains for production of citric acid or proteins are well characterized, this is not the case for the production of pectinases. We, therefore, systematically compared the pectinolytic capabilities of six A. niger strains (ATCC 1015, ATCC 11414, NRRL 3122, CBS 513.88, NRRL 3, and N402) using controlled batch cultivations in stirred-tank bioreactors. A. niger ATCC 11414 showed the highest polygalacturonase activity, specific protein secretion, and a suitable morphology. Furthermore, d-GalA release from sugar beet pulp was 75% higher compared to the standard lab strain A. niger N402. Our study, therefore, presents a robust initial strain selection to guide future process improvement of d-GalA production from agricultural residues and identifies a high-performance base strain for further genetic optimizations.
相似文献Simultaneous liquefaction, saccharification, and fermentation (SLSF) has attracted much attention for the production of bio-based chemicals, including l-lactic acid, due to its high efficiency and low cost. In this study, a lactic acid-producing bacterium with high tolerance of temperature up to 55 °C was isolated and characterized as Enterococcus faecalis DUT1805. Various strategies of stepwise controlled temperature were proposed and investigated for glucose utilization. The results indicated that E. faecalis DUT 1805 exhibited an optimal temperature at 50 °C, which could achieve temperature compatibility of enzyme, saccharification, and fermentation, and decrease the possibility of contamination by the other microorganisms during the large-scale fermentation. To reduce the cost of raw material and operation for lactic acid production, aging paddy rice with hull (APRH) was used in l-lactic acid production by simultaneous liquefaction, saccharification, and fermentation (SLSF). An open SLSF operation at 50 °C and pH 6.5, and 17% (w/v) solid loading in 5 L bioreactors was demonstrated with the lactic acid titer, yield, and productivity of 73.75 g/L, 87% to initial starch, and 2.17 g/(L h), respectively.
相似文献d-Erythrosyl aziridines were obtained from d-erythrosyl triazoles either by photolysis or through diazirine intermediates. These were found to undergo rich, high yielding chemistry by reaction with protic acids (HCl, BiI3/H2O and trifluoroacetic acid) leading to two types of furanoid sugar α-amino acids, and polyhydroxylprolines. Based on experimental evidence, reaction mechanisms have been proposed for the syntheses.
相似文献Iron deficiency is one of the most prevailing micronutrient deficiencies throughout the globe. Iron malnutrition affects billions of people around the world especially children and pregnant women. Its deficiencies can be overcome through microbial biofortification: a process of deliberately increasing desirable nutrients in crop plants. Plant growth-promoting rhizobacteria (PGPR) can improve iron content in edible plant tissues through different direct and indirect mechanisms. Adding plant growth regulators along with rhizobacteria makes it a novel fortification approach. In the current experiment, the interactive effect of two bacterial isolates (O-13 & K-10) alone and in consortium with l-tryptophan in the presence of iron sulfate was evaluated on growth, physiology, tuber characteristics, and iron concentration in potato (Solanum tuberosum L.). Results revealed that inoculation with PGPR and plant growth regulator (PGR) significantly improved the plant height, straw yield, and the number of tubers per plant. Potato (Solanum tuberosum L.) tuber characteristics (starch content, vitamin-C, relative water content) were also improved significantly. O-13, K-10, and l-tryptophan had significantly improved the iron concentration up to 20.59, 33.12, and 28.95%, respectively. However, inoculation with the microbial consortium and l-tryptophan showed a significant increase of up to one-fold in the iron concentration of potato (Solanum tuberosum L.) as compared with uninoculated control. The results suggest that rhizobacteria can help the plant to uptake nutrients from the soil. These findings concluded on the fact that the interactive effect of microbial assisted biofortification and plant growth regulator is a novel, promising, and cost-effective approach to mitigate micronutrient deficiencies especially in resource-limited countries.
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