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Branched-chain Amino Acids (branched-chain + amino_acids)
Selected AbstractsComplex phenotypes of a mutant inactivated for CymR, the global regulator of cysteine metabolism in Bacillus subtilisFEMS MICROBIOLOGY LETTERS, Issue 2 2010Marie-Françoise Hullo Abstract We characterized various phenotypes of a mutant inactivated for CymR, the master regulator of cysteine metabolism in Bacillus subtilis. The deletion of cymR resulted in impaired growth in the presence of cystine and increased sensitivity to hydrogen peroxide-, disulfide-, paraquat- and tellurite-induced stresses. Estimation of metabolite pools suggested that these phenotypes could be the result of profound metabolic changes in the ,cymR mutant including an increase of the intracellular cysteine pool and hydrogen sulfide formation, as well as a depletion of branched-chain amino acids. [source] Flavour formation by lactic acid bacteria and biochemical flavour profiling of cheese productsFEMS MICROBIOLOGY REVIEWS, Issue 3 2005Gerrit Smit Abstract Flavour development in dairy fermentations, most notably cheeses, results from a series of (bio)chemical processes in which the starter cultures provide the enzymes. Particularly the enzymatic degradation of proteins (caseins) leads to the formation of key-flavour components, which contribute to the sensory perception of dairy products. More specifically, caseins are degraded into peptides and amino acids and the latter are major precursors for volatile aroma compounds. In particular, the conversion of methionine, the aromatic and the branched-chain amino acids are crucial. A lot of research has focused on the degradation of caseins into peptides and free amino acids, and more recently, enzymes involved in the conversion of amino acids were identified. Most data are generated on Lactococcus lactis, which is the predominant organism in starter cultures used for cheese-making, but also Lactobacillus, Streptococcus, Propionibacterium and species used for surface ripening of cheeses are characterised in their flavour-forming capacity. In this paper, various enzymes and pathways involved in flavour formation will be highlighted and the impact of these findings for the development of industrial starter cultures will be discussed. [source] Restoration of innate host defense responses by oral supplementation of branched-chain amino acids in decompensated cirrhotic patientsHEPATOLOGY RESEARCH, Issue 12 2007Ikuo Nakamura Aim:, It has been reported that host defense responses, such as phagocytic function of neutrophils and natural killer (NK) cell activity of lymphocytes, are impaired in cirrhotic patients. The aim of the present study was to examine the effects of oral supplementation of branched-chain amino acids (BCAA) on host defense mechanisms in peripheral blood of patients with decompensated cirrhosis. Methods:, Ten patients with decompensated cirrhosis received 12 g BCAA daily for 3 months. Phagocytic function of neutrophils and NK activity of lymphocytes as well as serum albumin levels and Fisher's ratios were determined before and at 1 and 3 months of BCAA supplementation. For quantification of phagocytic function, fluorescent intensities of cells in the neutrophil region in the cytogram were determined by flow cytometry after incubation of whole blood with fluorescent microspheres. NK activity was estimated by 51Cr release assay using K-562 cell line as target cells. Results:, Phagocytic function of neutrophils was significantly improved by 3-month BCAA supplementation (P < 0.01). Thechanges of NK activity were also significant at 3 months of supplementation compared with before supplementation (P < 0.01). Fisher's ratios were significantly increased at 3 months of BCAA supplementation compared with those before oral supplementation (P < 0.05), although the changes of serum albumin level were not statistically significant. Conclusions:, BCAA oral supplementation improved phagocytic function of neutrophils and NK activity of lymphocytes in cirrhotic patients. BCAA supplementation may reduce the risk of bacterial and viral infection in patients with decompensated cirrhosis. [source] Enzymes involved in flavour formation by bacteria isolated from the smear population of surface-ripened cheeseINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 1 2004A G Williams Twenty-five bacterial isolates recovered from the surface population of smear-ripened cheese were assigned phenotypically as Brevibacterium spp., Corynebacterium spp. and Aureobacterium spp. using the Biolog GP2 microplate system and database. The range and activity of hydrolytic enzymes involved in the formation of cheese flavour constituents were monitored in cell-free lysates of the isolates. Esterase activity and the presence of a range of enzymes involved in amino acid release and breakdown was confirmed in all strains examined although there were pronounced interspecies and strain differences in the level of activity detected. Peptidolytic activities present in the smear bacteria included dipeptidyl peptidase and aminopeptidases that cleaved various N-terminal amino acids including proline. Subsequent breakdown of the released aromatic and branched-chain amino acids was mediated by ,-keto acid dependent aminotransferase action and several of the isolates were able to form thiols from sulphur-containing amino acid precursors. It was confirmed that the enzymic activity of the smear population could be manipulated by the use of defined starter cultures comprising selected combinations of smear isolates. The hydrolytic activities of the smear bacteria are involved in the generation of cheese flavour compounds and the enzyme profile is thus an important selection criterion for strains to be evaluated for use in defined surface smear preparations. [source] Expression of 3-hydroxyisobutyrate dehydrogenase in cultured neural cellsJOURNAL OF NEUROCHEMISTRY, Issue 4 2008Radovan Murín Abstract The branched-chain amino acids (BCAAs) , isoleucine, leucine, and valine , belong to the limited group of substances transported through the blood,brain barrier. One of the functions they are thought to have in brain is to serve as substrates for meeting parenchymal energy demands. Previous studies have shown the ubiquitous expression of a branched-chain alpha-keto acid dehydrogenase among neural cells. This enzyme catalyzes the initial and rate-limiting step in the irreversible degradative pathway for the carbon skeleton of valine and the other two branched-chain amino acids. Unlike the acyl-CoA derivates in the irreversible part of valine catabolism, 3-hydroxyisobutyrate could be expected to be released from cells by transport across the mitochondrial and plasma membranes. This could indeed be demonstrated for cultured astroglial cells. Therefore, to assess the ability of neural cells to make use of this valine-derived carbon skeleton as a metabolic substrate for the generation of energy, we investigated the expression in cultured neural cells of the enzyme processing this hydroxy acid, 3-hydroxyisobutyrate dehydrogenase (HIBDH). To achieve this, HIBDH was purified from bovine liver to serve as antigen for the production of an antiserum. Affinity-purified antibodies against HIBDH specifically recognized the enzyme in liver and brain homogenates. Immunocytochemistry demonstrated the ubiquitous expression of HIBDH among cultured glial (astroglial, oligodendroglial, microglial, and ependymal cells) and neuronal cells. Using an RT-PCR technique, these findings were corroborated by the detection of HIBDH mRNA in these cells. Furthermore, immunofluorescence double-labeling of astroglial cells with antisera against HIBDH and the mitochondrial marker pyruvate dehydrogenase localized HIBDH to mitochondria. The expression of HIBDH in neural cells demonstrates their potential to utilize valine imported into the brain for the generation of energy. [source] Regulation of branched-chain amino acid biosynthesis by ,-acetolactate decarboxylase in Streptococcus thermophilusLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2003C. Monnet Abstract Aims: To demonstrate the presence of an active , -acetolactate decarboxylase in Streptococcus thermophilus and to investigate its physiological function. Methods and Results:Streptococcus thermophilus CNRZ385 contains a gene encoding an , -acetolactate decarboxylase. Comparison of the production of , -acetolactate and its decarboxylation products, by the parent strain and an , -acetolactate decarboxylase-deficient mutant, demonstrated the presence of a control of the pool of ,-acetolactate by valine, leucine and isoleucine. This control occurs via an allosteric activation of the , -acetolactate decarboxylase. Cell-free extracts of S. thermophilus were not able to decarboxylate the isoleucine precursor , -acetohydroxybutyrate. Conclusions: These results strongly suggest that one of the physiological functions of the , -acetolactate decarboxylase in S. thermophilus is to regulate leucine and valine biosynthesis by diverting the flux of , -acetolactate towards acetoin when the branched-chain amino acids are present at a high concentration. Significance and Impact of the Study: Regulation of branched-chain amino acid biosynthesis by , -acetolactate decarboxylase may occur in several other micro-organisms and explain some of their growth properties. [source] Domino liver transplantation in maple syrup urine disease,LIVER TRANSPLANTATION, Issue 5 2006Ajai Khanna Liver transplantation has been reported in a few cases of maple syrup urine disease (MSUD), but is controversial. Many patients with approved indications for liver transplantation die before grafts are available. A 25-yr-old man with MSUD underwent liver transplantation, and his liver was used as a domino graft for a 53-yr-old man with hepatocellular carcinoma who had low priority on the liver transplant waiting list and was unlikely to survive until routine organ procurement. Both transplants were performed as "piggy back" procedures, reconstructing the domino graft with caval segments from the cadaveric donor. Neither required veno-venous bypass. Whole body leucine oxidation was estimated by 13CO2 in breath after oral boluses of L -[1- 13C]-leucine, before and after transplantation in both patients and a control subject. The surgical outcome was successful. The patient with MSUD had marked decreases in plasma branched-chain amino acids (BCAAs) and alloisoleucine (from 255 ± 66 to 16 ± 7 ,mol/L), despite advancement of dietary protein from 6 to >40 gm/day. The domino recipient maintained near-normal levels of plasma amino acids with no detectable alloisoleucine on unrestricted diet. Leucine oxidation increased in the patient with MSUD (from 2.2 to 5.6% recovered in 4 hours) and decreased in the recipient (from 9.7 to 6.2%). Neither patient demonstrated any apparent symptoms of MSUD over more than 7 months. In conclusion, liver transplantation substantially corrects whole body BCAA metabolism in MSUD and greatly attenuates the disease. Livers from patients with MSUD may be considered as domino grafts for patients who might otherwise not survive until transplantation. Liver Transpl 12:876,882, 2006. © 2006 AASLD. [source] Positive regulation of Bacillus subtilis ackA by CodY and CcpA: establishing a potential hierarchy in carbon flowMOLECULAR MICROBIOLOGY, Issue 3 2006Robert P. Shivers Summary Conversion of pyruvate to acetate via the phosphotransacetylase-acetate kinase pathway generates ATP and is a major overflow pathway under conditions of carbon and nitrogen excess. In Bacillus subtilis, this pathway is positively regulated by CcpA, a global regulator of carbon metabolism genes. Transcription of the acetate kinase gene (ackA) proved to be activated as well by a second global regulatory protein, CodY. Expression of an ackA,lacZ fusion was reduced in a codY mutant strain. CodY was found to bind in vitro to two sites in the ackA promoter region and to stimulate ackA transcription in a run-off transcription assay. This is the first known case of direct positive regulation by CodY. CodY and CcpA were found to bind to neighbouring sites and their effects were additive both in vivo and in vitro. Surprisingly, positive regulation by CodY, unlike repression, responded primarily to only one type of effector molecule. That is, branched-chain amino acids (BCAAs) served as more potent co-activators of CodY-dependent ackA transcription than did GTP. Given the roles of CcpA and CodY in regulating genes whose products determine the metabolic fate of pyruvate, these two proteins may act together to mediate a hierarchical conversion of pyruvate to its many potential products. [source] Multiple determinants influence root colonization and induction of induced systemic resistance by Pseudomonas chlororaphis O6MOLECULAR PLANT PATHOLOGY, Issue 6 2006SONG HEE HAN SUMMARY Colonization of the roots of tobacco by Pseudomonas chlororaphis O6 induces systemic resistance to the soft-rot pathogen, Erwinia carotovora ssp. carotovara SCC1. A screen of the transposon mutants of P. chlororaphis O6 showed mutants with about a fivefold reduction in ability to induce systemic resistance to the soft-rot disease. These mutations disrupted genes involved in diverse functions: a methyl-accepting chemotaxis protein, biosynthesis of purines, phospholipase C, transport of branched-chain amino acids and an ABC transporter. Additional mutations were detected in the intergenic spacer regions between genes encoding a GGDEF protein and fumarate dehydratase, and in genes of unknown function. The mutants in the ABC transporters did not display reduced root colonization. However, the other mutants had up to 100-fold reduced colonization levels. Generally the production of metabolites important for interactions in the rhizosphere, phenazines and siderophores, was not altered by the mutations. A reduced induction of systemic resistance by a purine biosynthesis mutant with a disrupted purM gene correlated with poor growth rate, lesser production of phenazines and siderophore and low levels of root colonization. These studies showed that multiple determinants are involved in the induction of systemic resistance, with there being a requirement for strong root colonization. [source] Proteomic analysis of hearts from frataxin knockout mice: Marked rearrangement of energy metabolism, a response to cellular stress and altered expression of proteins involved in cell structure, motility and metabolismPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 8 2008Robert Sutak Abstract A frequent cause of death in Friedreich's ataxia patients is cardiomyopathy, but the molecular alterations underlying this condition are unknown. We performed 2-DE to characterize the changes in protein expression of hearts using the muscle creatine kinase frataxin conditional knockout (KO) mouse. Pronounced changes in protein expression profile were observed in 9,week-old KO mice with severe cardiomyopathy. In contrast, only several proteins showed altered expression in asymptomatic 4,week-old KO mice. In hearts from frataxin KO mice, components of the iron-dependent complex-I and -II of the mitochondrial electron transport chain and enzymes involved in ATP homeostasis (creatine kinase, adenylate kinase) displayed decreased expression. Interestingly, the KO hearts exhibited increased expression of enzymes involved in the citric acid cycle, catabolism of branched-chain amino acids, ketone body utilization and pyruvate decarboxylation. This constitutes evidence of metabolic compensation due to decreased expression of electron transport proteins. There was also pronounced up-regulation of proteins involved in stress protection, such as a variety of chaperones, as well as altered expression of proteins involved in cellular structure, motility and general metabolism. This is the first report of the molecular changes at the protein level which could be involved in the cardiomyopathy of the frataxin KO mouse. [source] Changes in Plasma Amino Acids During Extracorporeal Liver Support by Fractionated Plasma Separation and AdsorptionARTIFICIAL ORGANS, Issue 2 2010Kinan Rifai Abstract In patients with liver failure, amino acid dysbalance is common and associated with hepatic encephalopathy. Prometheus is a newly designed extracorporeal liver support system based upon fractionated plasma separation and adsorption (FPSA). We evaluated the influence of FPSA on plasma amino acid patterns in patients with liver failure and hepatic encephalopathy. We studied nine patients with acute-on-chronic liver failure, hepatic encephalopathy, and concomitant renal failure. A single session of FPSA therapy for 5 ± 1 h was performed in all patients. Twenty-six different plasma amino acids were measured by high-performance liquid chromatography before and after FPSA treatment. Total amino acids as well as Fischer index were calculated. Additionally, a variety of clinical and biochemical parameters were assessed. Before FPSA was started, plasma levels of most amino acids were elevated. Plasma ammonia levels correlated with glutamine levels (P < 0.04). During FPSA, plasma levels of nearly all amino acids significantly decreased except for branched-chain amino acids. The Fischer index improved without reaching statistical significance. FPSA therapy tends to normalize plasma amino acids in patients with combined liver and renal failure. This may contribute to positive pathophysiologic effects, especially on hepatic encephalopathy. However, the clinical significance of these findings needs to be further evaluated. [source] Facile crystallization of Escherichia coli ketol-acid reductoisomeraseACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2004Jennifer A. McCourt Ketol-acid reductoisomerase (EC 1.1.1.86) catalyses the second reaction in the biosynthesis of branched-chain amino acids. The reaction involves an Mg2+ -dependent alkyl migration followed by an NADPH-dependent reduction of the 2-keto group. Here, the crystallization of the Escherichia coli enzyme is reported. A form with a C-terminal hexahistidine tag could be crystallized under 18 different conditions in the absence of NADPH or Mg2+ and a further six crystallization conditions were identified with one or both ligands. With the hexahistidine tag on the N-terminus, 20 crystallization conditions were found, some of which required the presence of NADPH, NADP+, Mg2+ or a combination of ligands. Finally, the selenomethionine-substituted enzyme with the N-terminal tag crystallized under 15 conditions. Thus, the enzyme is remarkably easy to crystallize. Most of the crystals diffract poorly but several data sets were collected at better than 3.2,Å resolution; attempts to phase them are currently in progress. [source] Identification of Urinary Biomarkers Useful for Distinguishing a Difference in Mechanism of Toxicity in Rat Model of CholestasisBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 3 2009Kenji Ishihara To inhibit biliary secretion of bile, cyclosporine A was administered to male Sprague,Dawley rats. Obstruction of bile flow was induced by administration of 4,4,-methylene dianiline, ,-naphthylisothiocyanate or bile duct ligation. Clinical pathological and histopathological examinations were performed to confirm cholestatic injury and 1H nuclear magnetic resonance spectral data for urine samples were analysed to determine similarities and differences in profiles of metabolites using the Spotfire®. In cyclosporine A-treated groups, serum total bilirubin and bile acid were significantly increased but no remarkable hepatic histopathological-changes were observed. In 4,4,-methylene dianiline-, ,-naphthylisothiocyanate- and bile duct ligation-treated groups, serum alkaline phosphatase, ,-glutamyltranspeptidase and total bilirubin levels increased significantly, and hepatic histopathological-changes were observed. On urinary 1H nuclear magnetic resonance spectral analysis, area intensities derived from 0.66 to 1.90 ppm were decreased by cyclosporine A, whereas they were increased by other treatments. These metabolites were identified using the NMR suite® as bile acids, branched-chain amino acids, n-butyrate, propionate, methyl malonate and valerate. These metabolites were further investigated by K-means clustering analysis. The cluster of these metabolites is considered to be altered by cholestasis. We conclude that bile acids, valine and methyl malonate have a possibility to be urinary cholestatic biomarkers, which distinguish a difference in mechanism of toxicity. 1H nuclear magnetic resonance metabonomics thus appears to be useful for determining the mechanisms of toxicity and can be front-loaded in drug safety evaluation and biomarker discovery. [source] The 1.9,Å structure of the branched-chain amino-acid transaminase (IlvE) from Mycobacterium tuberculosisACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2009L. W. Tremblay Unlike mammals, bacteria encode enzymes that synthesize branched-chain amino acids. The pyridoxal 5,-phosphate-dependent transaminase performs the final biosynthetic step in these pathways, converting keto acid precursors into ,-amino acids. The branched-chain amino-acid transaminase from Mycobacterium tuberculosis (MtIlvE) has been crystallized and its structure has been solved at 1.9,Å resolution. The MtIlvE monomer is composed of two domains that interact to form the active site. The biologically active form of IlvE is a homodimer in which each monomer contributes a substrate-specificity loop to the partner molecule. Additional substrate selectivity may be imparted by a conserved N-terminal Phe30 residue, which has previously been observed to shield the active site in the type IV fold homodimer. The active site of MtIlvE contains density corresponding to bound PMP, which is likely to be a consequence of the presence of tryptone in the crystallization medium. Additionally, two cysteine residues are positioned at the dimer interface for disulfide-bond formation under oxidative conditions. It is unknown whether they are involved in any regulatory activities analogous to those of the human mitochondrial branched-chain amino-acid transaminase. [source] A double-blind randomized clinical trial in amyotrophic lateral sclerosis using lamotrigine: effects on CSF glutamate, aspartate, branched-chain amino acid levels and clinical parametersACTA NEUROLOGICA SCANDINAVICA, Issue 1 2003H. Ryberg Objectives , A study was conducted to examine the effect of lamotrigine (LTG) in amyotrophic lateral sclerosis (ALS). Material and methods , Patients were entered in a double-blind, placebo-controlled, crossover study. None of the patients were treated with riluzole, which was not approved for treatment of ALS in Sweden when the study started. After randomization, each patient was treated with placebo or LTG 300 mg daily, followed by a washout period and a second treatment period. Results , Thirty patients completed the study and were included in the analysis of the primary outcome, which was measured with clinical scales. The cerebrospinal fluid (CSF) levels of glutamate, aspartate, branched-chain amino acids and LTG were also measured. Changes for glutamate, valine and LTG were found during the progression of the disease. The clinical parameters and the levels of CSF amino acids were similar for the two treatment groups. Conclusion , No clinical effect of LTG on ALS progression could be found. [source] Interventions for apnoea of prematurity: a personal viewACTA PAEDIATRICA, Issue 2 2010CF Poets Abstract Aim:, To review treatments for apnoea of prematurity (AOP). Methods:, Literature Review and description of personal practice. Results:, Provided that symptomatic apnoea has been ruled out, interventions to improve AOP can be viewed as directed at one of three underlying mechanisms: (i) a reduced work of breathing [e.g. prone positioning, nasal continuous positive airway pressure (CPAP)], (ii) an increased respiratory drive (e.g. caffeine), and (iii) an improved diaphragmatic function (e.g. branched-chain amino acids). Most options currently applied, however, have not yet been shown to be effective and/or safe, except for prone, head-elevated positioning, synchronized nasal ventilation/CPAP, and caffeine. Conclusion:, Treatment usually follows an incremental approach, starting with positioning, followed by caffeine (which should be started early, at least in infants <1250 g), and nasal ventilation or CPAP via variable flow systems that reduce work of breathing. From a research point of view, we most urgently need data on the frequency and severity of bradycardia and intermittent hypoxia that can yet be tolerated without putting an infant at risk of impaired development or retinopathy of prematurity. [source] | ||||||||||||||||