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Amino Acid Synthesis (amino + acid_synthesis)
Selected AbstractsFree Radical-Mediated Aryl Amination and Its Use in a Convergent [3 + 2] Strategy for Enantioselective Indoline ,-Amino Acid Synthesis.CHEMINFORM, Issue 22 2003Rajesh Viswanathan Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Scope and Limitations in the Use of N-(PhF)Serine-Derived Cyclic Sulfamidates for Amino Acid Synthesis.CHEMINFORM, Issue 41 2001Lan Wei Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Mutational analysis of mononucleotide repeats in dual specificity tyrosine phosphatase genes in gastric and colon carcinomas with microsatellite instabilityAPMIS, Issue 5 2010SANG YONG SONG Song SY, Kang MR, Yoo NJ, Lee SH. Mutational analysis of mononucleotide repeats in dual specificity tyrosine phosphatase genes in gastric and colon carcinomas with microsatellite instability. APMIS 2010; 118: 389,93. Coordinated protein phosphorylation and dephosphorylation are crucial in the regulation of cell signaling, and disruption of the coordination is known to play important roles in cancer development. Recent reports revealed that classical protein tyrosine phosphatase (PTP)-encoded genes are somatically mutated in human colorectal cancer. However, data on dual specificity phosphatase (DPTP) gene mutations in human cancers are lacking. By analyzing a public genomic database, we found that five DPTP genes, CDC14A, MTM1, MTMR3, SSH1, and SSH2, have mononucleotide repeats in their coding DNA sequences. To see whether these genes are mutated in cancers with microsatellite instability (MSI), we analyzed the mononucleotide repeats in 26 gastric cancers (GC) with MSI (MSI-H), 12 GC with low MSI (MSI-L), 45 GC with stable MSI (MSS), 33 colorectal cancers (CRC) with MSI-H, 14 CRC with MSI-L, and 45 CRC with MSS by single-strand conformation polymorphism (SSCP). We found CDC14A and MTMR3 mutations in five and one cancer (s), respectively. These mutations were detected in MSI-H cancers, but not in MSI-L or MSS cancers. The GC and CRC with MSI-H harbored the mutations in 15% and 6%, respectively. The CDC14A and MTMR3 mutations detected in the GC and CRC were deletion or duplication mutations of one base in the nucleotide repeats that would result in premature stops of the amino acid syntheses. Our data show that frameshift mutations of DPTP genes in MSI-H cancers occur at moderate frequencies. The data suggested that alterations in the CDC14A and MTMR3 genes may play a role in the development of GC and CRC with MSI-H by deregulating phosphatase functions possibly together with mutations of classical PTP genes. [source] Growth-induced changes in the proteome of Helicobacter pyloriELECTROPHORESIS, Issue 5-6 2006Christina Uwins Abstract Helicobacter pylori is a major human pathogen that is responsible for a number of gastrointestinal infections. We have used 2-DE to characterise protein synthesis in bacteria grown either on solid agar-based media or in each of two broth culture media (Brucella and brain heart infusion (BHI) broth). Significant differences were observed in the proteomes of bacteria grown either on agar-based or in broth media. Major changes in protein abundance were identified using principal component analysis (PCA), which delineated the profiles derived for the three key growth conditions (i.e. agar plates, Brucella and BHI broth). Proteins detected across the gel series were identified by peptide mass mapping and Edman sequencing. A number of proteins associated with protein synthesis in general as well as specific amino acid synthesis were depressed in broth-grown bacteria compared to plate-grown bacteria. A similar reduction was also observed in the abundance of proteins involved in detoxification. Two of the most abundant spots, identified as UreB and GroEL, in plate-grown bacteria showed a >140-fold drop in abundance in bacteria grown in Brucella broth compared to bacteria grown on agar plates. Two protein spots induced in bacteria grown in broth culture were both identified as glyceraldehyde 3-phosphate dehydrogenase based on their N -terminal amino acid sequences derived by Edman degradation. The underlying causes of the changes in the proteins abundance were not clear, but it was likely that a significant proportion of the changes were due to the alkaline pH of the broth culture media. [source] Implication of the glutamine synthetase/glutamate synthase pathway in conditioning the amino acid metabolism in bundle sheath and mesophyll cells of maize leavesFEBS JOURNAL, Issue 12 2008Marie-Hélène Valadier We investigated the role of glutamine synthetases (cytosolic GS1 and chloroplast GS2) and glutamate synthases (ferredoxin-GOGAT and NADH-GOGAT) in the inorganic nitrogen assimilation and reassimilation into amino acids between bundle sheath cells and mesophyll cells for the remobilization of amino acids during the early phase of grain filling in Zea mays L. The plants responded to a light/dark cycle at the level of nitrate, ammonium and amino acids in the second leaf, upward from the primary ear, which acted as the source organ. The assimilation of ammonium issued from distinct pathways and amino acid synthesis were evaluated from the diurnal rhythms of the transcripts and the encoded enzyme activities of nitrate reductase, nitrite reductase, GS1, GS2, ferredoxin-GOGAT, NADH-GOGAT, NADH-glutamate dehydrogenase and asparagine synthetase. We discerned the specific role of the isoproteins of ferredoxin and ferredoxin:NADP+ oxidoreductase in providing ferredoxin-GOGAT with photoreduced or enzymatically reduced ferredoxin as the electron donor. The spatial distribution of ferredoxin-GOGAT supported its role in the nitrogen (re)assimilation and reallocation in bundle sheath cells and mesophyll cells of the source leaf. The diurnal nitrogen recycling within the plants took place via the specific amino acids in the phloem and xylem exudates. Taken together, we conclude that the GS1/ferredoxin-GOGAT cycle is the main pathway of inorganic nitrogen assimilation and recycling into glutamine and glutamate, and preconditions amino acid interconversion and remobilization. [source] Stereoselective biosynthesis of chloroarylpropane diols by the basidiomycete Bjerkandera adusta: exploring the roles of amino acids, pyruvate, glycerol and phenyl acetyl carbinolFEMS MICROBIOLOGY LETTERS, Issue 1 2003Peter James Silk Abstract Bjerkandera adusta produces many chlorometabolites including chlorinated anisyl metabolites (CAMs) and 1-arylpropane-1,2-diols (1, 2, 3, 4) as idiophasic metabolic products of l -phenylalanine. These diols are stereoselectively biosynthesized from a C7 -unit (benzylic, from l -phenylalanine) and a C2 -unit, of unknown origin, as predominantly erythro (1R,2S) enantiomers. Of the labeled amino acids tested as possible C2 -units, at the 4,10 mM level, none were found to efficiently label the 2,3-propane carbons of the diols. However, glycine (2- 13C), l -serine (2,3,3-d3) and l -methionine (methyl-d3) entered the biomethylation pathway. Neither pyruvate (2,3- 13C2), acetate (1,2- 13C2), acetaldehyde (d4) nor ethanol (ethyl-d5) labeled the 2,3-propane carbons of the diols at the 4,10 mM level. Pyruvate (2,3- 13C2) and l -serine (2,3,3-d3) (which also entered the biomethylation pathway) did, however, effectively label the 2,3-propane carbons of the ,-ketols and diols at the 40 mM level as evidenced by mass spectrometry. Glycerol (1,1,2,3,3-d5) also appeared to label one of the 2,3-propane carbons (ca. 5% as 2H2 in the C3 side chain) as suggested by mass spectrometric data and also entered the biomethylation pathway, likely via amino acid synthesis. Glycerol (through pyruvate), therefore, likely supplies C2 and C3 of the propane side chain with arylpropane diol biosynthesis. Incubation of B. adusta with synthetic [2- 2H1,2- 18O]-glycerol showed that neither 2H nor 18O were incorporated in the ,-ketols or diols. The oxygen atom on the C2 of the ketols/diols, therefore, does not appear to come from the oxygen atom on the C2 of glycerol. Glycerol, however, can readily form l -serine (which can then form pyruvate via PLP/serine dehydratase and involve transamination washing out the 18O label and providing the oxygen from water), and can then go on to label the C2 -unit. Labeled ,-ketol, phenyl acetyl carbinol (5) (PAC; ring-d5, 2,3- 13C2 propane) cultured with B. adusta leads to stereospecific reduction to the (1R,2S)-diol (6) (ring-d5 and 2,3- 13C2); in all other metabolites produced, the 2,3- 13C2 label is washed out. Incubation of the fungus with 4-fluorobenzaldehyde (13) produces a pooling of predominantly erythro (1R,2S) 1-(4,-fluorophenyl)-1,2-propane diol (18 as diacetate) (through the corresponding ,-ketols 16, 17). Blocking the para-position with fluorine thus appears to prevent ring oxygenation and also chlorination, forcing the conclusion that para-ring oxygenation precedes meta-chlorination. [source] Autophagy and amino acid homeostasis are required for chronological longevity in Saccharomyces cerevisiaeAGING CELL, Issue 4 2009Ashley L. Alvers Summary Following cessation of growth, yeast cells remain viable in a nondividing state for a period of time known as the chronological lifespan (CLS). Autophagy is a degradative process responsible for amino acid recycling in response to nitrogen starvation and amino acid limitation. We have investigated the role of autophagy during chronological aging of yeast grown in glucose minimal media containing different supplemental essential and nonessential amino acids. Deletion of ATG1 or ATG7, both of which are required for autophagy, reduced CLS, whereas deletion of ATG11, which is required for selective targeting of cellular components to the vacuole for degradation, did not reduce CLS. The nonessential amino acids isoleucine and valine, and the essential amino acid leucine, extended CLS in autophagy-deficient as well as autophagy-competent yeast. This extension was suppressed by constitutive expression of GCN4, which encodes a transcriptional regulator of general amino acid control (GAAC). Consistent with this, GCN4 expression was reduced by isoleucine and valine. Furthermore, elimination of the leucine requirement extended CLS and prevented the effects of constitutive expression of GCN4. Interestingly, deletion of LEU3, a GAAC target gene encoding a transcriptional regulator of branched side chain amino acid synthesis, dramatically increased CLS in the absence of amino acid supplements. In general, this indicates that activation of GAAC reduces CLS whereas suppression of GAAC extends CLS in minimal medium. These findings demonstrate important roles for autophagy and amino acid homeostasis in determining CLS in yeast. [source] Region-selective alterations of glucose oxidation and amino acid synthesis in the thiamine-deficient rat brain: a re-evaluation using 1H/13C nuclear magnetic resonance spectroscopyJOURNAL OF NEUROCHEMISTRY, Issue 2 2008Darren Navarro Abstract Thiamine deficiency provides an effective model of selective neuronal cell death. 1H and 13C-NMR was used to investigate the effects of thiamine deficiency on the synthesis of amino acids derived from [1- 13C]glucose in vulnerable (medial thalamus; MT) compared to non-vulnerable (frontal cortex; FC) brain regions. Following 11 days of thiamine deficiency, a time-point associated with the absence of significant neuronal cell death, regional concentrations of glutamate, glutamine and GABA remained unaffected in FC and MT; however, decreased levels of aspartate in MT at this time-point were a predictor of regional vulnerability. De novo synthesis of glutamate and GABA were unaffected at 11 days of thiamine deficiency, while synthesis of [2- 13C]aspartate was significantly impaired. Glucose loading, which has been shown to exacerbate symptoms in patients with thiamine deficiency, resulted in further decreases of TCA cycle flux and reduced de novo synthesis of glutamate, aspartate and GABA in thiamine-deficient (TD) rats. Isotopomer analysis revealed that impaired TCA cycle flux and decreased aspartate synthesis due to thiamine deficiency occurred principally in neurons. Glucose loading deteriorated TD-related decreases in TCA cycle flux, and concomitantly reduced synthesis of aspartate and glutamate in MT. [source] Effect of Veillonella parvula on the antimicrobial resistance and gene expression of Streptococcus mutans grown in a dual-species biofilmMOLECULAR ORAL MICROBIOLOGY, Issue 3 2008S. B. I. Luppens Introduction:, Our previous studies showed that Streptococcus mutans and Veillonella parvula dual-species biofilms have a different acid production profile and a higher resistance to chlorhexidine than their single-species counterparts. The aim of the current study was to test whether the susceptibility of S. mutans grown in the presence of V. parvula is also decreased when it is exposed to various other antimicrobials. Furthermore, the aim was to identify other changes in the physiology of S. mutans when V. parvula was present using transcriptomics. Methods:, Susceptibility to antimicrobials was assessed in killing experiments. Transcript levels in S. mutans were measured with the help of S. mutans microarrays. Results:, When V. parvula was present, S. mutans showed an increase in survival after exposure to various antimicrobials. Furthermore, this co-existence altered the physiology of S. mutans. The expression of genes coding for proteins involved in amino acid synthesis, the signal recognition particle-translocation pathway, purine metabolism, intracellular polysaccharide synthesis, and protein synthesis all changed. Conclusion:, Growing in a biofilm together with a non-pathogenic bacterium like V. parvula changes the physiology of S. mutans, and gives this bacterium an advantage in surviving antimicrobial treatment. Thus, the study of pathogens implicated in polymicrobial diseases, such as caries and periodontitis, should be focused more on multispecies biofilms. In addition, the testing of susceptibility to currently used and new antimicrobials should be performed on a multispecies microbial community rather than with single pathogens. [source] Proteomic analysis of growth phase-dependent proteins of Streptococcus pneumoniaePROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 4 2006Kwang-Jun Lee Abstract Streptococcus pneumoniae is an important human pathogen that causes a variety of diseases, such as pneumonia, bacteremia, meningitis, otitis media, and sinusitis, in both adults and children. The global pattern of growth phase-dependent protein expression of S. pneumoniae during in vitro culture was analyzed using 2-DE combined with MALDI-TOF MS and LC/ESI-MS/MS. Several protein production patterns were observed at four time points throughout the growth stage, although some protein levels did not change significantly. We focused on the switch in protein expression at the transition from log growth phase to stationary phase. Proteins that were significantly induced or repressed at this point are likely to be involved in central intermediary metabolism, amino acid synthesis, nucleotide, and fatty acid metabolism, cell wall synthesis, protein degradation, and stress responses. This global expression profiling approach has revealed previously unrecognized relationships between proteins in the life of this pathogen. [source] Stable isotope analysis of modern human hair collected from Asia (China, India, Mongolia, and Pakistan)AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2010A.H. Thompson Abstract We report isotopic data (,2H, ,18O n = 196; ,13C, ,15N n = 142; ,34S n = 85) from human hair and drinking water (,2H, ,18O n = 67) collected across China, India, Mongolia, and Pakistan. Hair isotope ratios reflected the large environmental isotopic gradients and dietary differences. Geographic information was recorded in H and O and to a lesser extent, S isotopes. H and O data were entered into a recently developed model describing the relationship between the H and O isotope composition of human hair and drinking water in modern USA and pre-globalized populations. This has anthropological and forensic applications including reconstructing environment and diet in modern and ancient human hair. However, it has not been applied to a modern population outside of the USA, where we expect different diet. Relationships between H and O isotope ratios in drinking water and hair of modern human populations in Asia were different to both modern USA and pre-globalized populations. However, the Asian dataset was closer to the modern USA than to pre-globalized populations. Model parameters suggested slightly higher consumption of locally producedfoods in our sampled population than modern USA residents, but lower than pre-globalized populations. The degree of in vivo amino acid synthesis was comparable to both the modern USA and pre-globalized populations. C isotope ratios reflected the predominantly C3 -based regional agriculture and C4 consumption in northernChina. C, N, and S isotope ratios supported marine food consumption in some coastal locales. N isotope ratios suggested a relatively low consumption of animal-derived products compared to western populations. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source] Increasing amino acid supply in pea embryos reveals specific interactions of N and C metabolism, and highlights the importance of mitochondrial metabolismTHE PLANT JOURNAL, Issue 6 2008Kathleen Weigelt Summary The application of nitrogen to legumes regulates seed metabolism and composition. We recently showed that the seed-specific overexpression of amino acid permease VfAAP1 increases amino acid supply, and the levels of N and protein in the seeds. Two consecutive field trials using Pisum sativum AAP1 lines confirmed increases in the levels of N and globulin in seed; however, compensatory changes of sucrose/starch and individual seed weight were also observed. We present a comprehensive analysis of AAP1 seeds using combinatorial transcript and metabolite profiling to monitor the effects of nitrogen supply on seed metabolism. AAP1 seeds have increased amino acids and stimulated gene expression associated with storage protein synthesis, maturation, deposition and vesicle trafficking. Transcript/metabolite changes reveal the channelling of surplus N into the transient storage pools asparagine and arginine, indicating that asparagine synthase is transcriptionally activated by high N levels and/or C limitation. Increased C-acceptor demand for amino acid synthesis, resulting from elevated levels of N in seeds, initiates sucrose mobilization and sucrose-dependent pathways via sucrose synthase, glycolysis and the TCA cycle. The AAP1 seeds display a limitation in C, which leads to the catabolism of arginine, glutamic acid and methionine to putrescine, ,-alanine and succinate. Mitochondria are involved in the coordination of C/N metabolism, with branched-chain amino acid catabolism and a ,-amino-butyric acid shunt. AAP1 seeds contain higher levels of ABA, which is possibly involved in storage-associated gene expression and the N-dependent stimulation of sucrose mobilization, indicating that a signalling network of C, N and ABA is operating during seed maturation. These results demonstrate that legume seeds have a high capacity to regulate N:C ratios, and highlight the importance of mitochondria in the control of N,C balance and amino acid homeostasis. [source] Importance of NADPH supply for improved L -valine formation in Corynebacterium glutamicumBIOTECHNOLOGY PROGRESS, Issue 2 2010Tobias Bartek Abstract Cofactor recycling is known to be crucial for amino acid synthesis. Hence, cofactor supply was now analyzed for L -valine to identify new targets for an improvement of production. The central carbon metabolism was analyzed by stoichiometric modeling to estimate the influence of cofactors and to quantify the theoretical yield of L -valine on glucose. Three different optimal routes for L -valine biosynthesis were identified by elementary mode (EM) analysis. The modes differed mainly in the manner of NADPH regeneration, substantiating that the cofactor supply may be crucial for efficient L -valine production. Although the isocitrate dehydrogenase as an NADPH source within the tricarboxylic acid cycle only enables an L -valine yield of YVal/Glc = 0.5 mol L -valine/mol glucose (mol Val/mol Glc), the pentose phosphate pathway seems to be the most promising NADPH source. Based on the theoretical calculation of EMs, the gene encoding phosphoglucoisomerase (PGI) was deleted to achieve this EM with a theoretical yield YVal/Glc = 0.86 mol Val/mol Glc during the production phase. The intracellular NADPH concentration was significantly increased in the PGI-deficient mutant. L -Valine yield increased from 0.49 ± 0.13 to 0.67 ± 0.03 mol Val/mol Glc, and, concomitantly, the formation of by-products such as pyruvate was reduced. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] | ||||||||||||||||