The Experts below are selected from a list of 36 Experts worldwide ranked by ideXlab platform

Klaus J Petzke - One of the best experts on this subject based on the ideXlab platform.

  • the dietary protein paradox and Threonine 15 n depletion pyridoxal 5 phosphate enzyme activity as a mechanism for the δ 15 n trophic level effect
    Rapid Communications in Mass Spectrometry, 2017
    Co-Authors: Benjamin T Fuller, Klaus J Petzke
    Abstract:

    Rationale Nitrogen stable isotope ratios (δ15 N values) are used to reconstruct dietary patterns, but the biochemical mechanism(s) responsible for the diet to tissue trophic level effect and its variability are not fully understood. Here δ15 N amino acid (AA) values and physiological measurements (nitrogen intake, plasma albumin concentrations, liver-reduced glutathione concentrations and leucine oxidation rates) are used to investigate increased dietary protein consumption and oxidative stress (vitamin E deficiency) in rat total plasma protein. Methods Using gas chromatography/combustion/isotope ratio mass spectrometry, the δ15 N values from N-pivaloyl-i-propyl esters of 15 AAs are reported for rats (n = 40) fed casein-based diets with: adequate protein (AP, 13.8%; n = 10), medium protein (MP, 25.7%; n = 10), high protein (HP, 51.3%; n = 10) or HP without vitamin E (HP-E; n = 10) for 18 weeks. Results Between the HP and AP groups, the δ15 NAA values of Threonine (-4.0‰), serine (+1.4‰) and glycine (+1.2‰) display the largest differences and show significant correlations with: nitrogen intake, plasma albumin concentrations, liver-reduced glutathione concentrations and leucine oxidation rates. This indicates increased AA catabolism by the dietary induction of shared common metabolic pathways involving the enzymes Threonine Ammonia-Lyase (EC 4.3.1.19), serine hydroxymethyltransferase (EC 2.1.2.1) and the glycine cleavage system (EC 2.1.2.10). The δ15 NAA values of the HP-E and HP groups were not found to be significantly different. Conclusions The 15 N-depleted results of Threonine are linked to increased activity of Threonine Ammonia-Lyase, and show potential as a possible biomarker for protein intake and/or gluconeogenesis. We hypothesize that the inverse nitrogen equilibrium isotope effects of Schiff base formation, between AAs and pyridoxal-5'-phosphate cofactor enzymes, play a key role in the bioaccumulation and depletion of 15 N in the biomolecules of living organisms and contributes to the variability in the nitrogen trophic level effect. Copyright © 2017 John Wiley & Sons, Ltd.

  • the dietary protein paradox and Threonine 15n depletion pyridoxal 5 phosphate enzyme activity as a mechanism for the δ15n trophic level effect
    Rapid Communications in Mass Spectrometry, 2017
    Co-Authors: Benjamin T Fuller, Klaus J Petzke
    Abstract:

    Rationale Nitrogen stable isotope ratios (δ15 N values) are used to reconstruct dietary patterns, but the biochemical mechanism(s) responsible for the diet to tissue trophic level effect and its variability are not fully understood. Here δ15 N amino acid (AA) values and physiological measurements (nitrogen intake, plasma albumin concentrations, liver-reduced glutathione concentrations and leucine oxidation rates) are used to investigate increased dietary protein consumption and oxidative stress (vitamin E deficiency) in rat total plasma protein. Methods Using gas chromatography/combustion/isotope ratio mass spectrometry, the δ15 N values from N-pivaloyl-i-propyl esters of 15 AAs are reported for rats (n = 40) fed casein-based diets with: adequate protein (AP, 13.8%; n = 10), medium protein (MP, 25.7%; n = 10), high protein (HP, 51.3%; n = 10) or HP without vitamin E (HP-E; n = 10) for 18 weeks. Results Between the HP and AP groups, the δ15 NAA values of Threonine (-4.0‰), serine (+1.4‰) and glycine (+1.2‰) display the largest differences and show significant correlations with: nitrogen intake, plasma albumin concentrations, liver-reduced glutathione concentrations and leucine oxidation rates. This indicates increased AA catabolism by the dietary induction of shared common metabolic pathways involving the enzymes Threonine Ammonia-Lyase (EC 4.3.1.19), serine hydroxymethyltransferase (EC 2.1.2.1) and the glycine cleavage system (EC 2.1.2.10). The δ15 NAA values of the HP-E and HP groups were not found to be significantly different. Conclusions The 15 N-depleted results of Threonine are linked to increased activity of Threonine Ammonia-Lyase, and show potential as a possible biomarker for protein intake and/or gluconeogenesis. We hypothesize that the inverse nitrogen equilibrium isotope effects of Schiff base formation, between AAs and pyridoxal-5'-phosphate cofactor enzymes, play a key role in the bioaccumulation and depletion of 15 N in the biomolecules of living organisms and contributes to the variability in the nitrogen trophic level effect. Copyright © 2017 John Wiley & Sons, Ltd.

Benjamin T Fuller - One of the best experts on this subject based on the ideXlab platform.

  • the dietary protein paradox and Threonine 15 n depletion pyridoxal 5 phosphate enzyme activity as a mechanism for the δ 15 n trophic level effect
    Rapid Communications in Mass Spectrometry, 2017
    Co-Authors: Benjamin T Fuller, Klaus J Petzke
    Abstract:

    Rationale Nitrogen stable isotope ratios (δ15 N values) are used to reconstruct dietary patterns, but the biochemical mechanism(s) responsible for the diet to tissue trophic level effect and its variability are not fully understood. Here δ15 N amino acid (AA) values and physiological measurements (nitrogen intake, plasma albumin concentrations, liver-reduced glutathione concentrations and leucine oxidation rates) are used to investigate increased dietary protein consumption and oxidative stress (vitamin E deficiency) in rat total plasma protein. Methods Using gas chromatography/combustion/isotope ratio mass spectrometry, the δ15 N values from N-pivaloyl-i-propyl esters of 15 AAs are reported for rats (n = 40) fed casein-based diets with: adequate protein (AP, 13.8%; n = 10), medium protein (MP, 25.7%; n = 10), high protein (HP, 51.3%; n = 10) or HP without vitamin E (HP-E; n = 10) for 18 weeks. Results Between the HP and AP groups, the δ15 NAA values of Threonine (-4.0‰), serine (+1.4‰) and glycine (+1.2‰) display the largest differences and show significant correlations with: nitrogen intake, plasma albumin concentrations, liver-reduced glutathione concentrations and leucine oxidation rates. This indicates increased AA catabolism by the dietary induction of shared common metabolic pathways involving the enzymes Threonine Ammonia-Lyase (EC 4.3.1.19), serine hydroxymethyltransferase (EC 2.1.2.1) and the glycine cleavage system (EC 2.1.2.10). The δ15 NAA values of the HP-E and HP groups were not found to be significantly different. Conclusions The 15 N-depleted results of Threonine are linked to increased activity of Threonine Ammonia-Lyase, and show potential as a possible biomarker for protein intake and/or gluconeogenesis. We hypothesize that the inverse nitrogen equilibrium isotope effects of Schiff base formation, between AAs and pyridoxal-5'-phosphate cofactor enzymes, play a key role in the bioaccumulation and depletion of 15 N in the biomolecules of living organisms and contributes to the variability in the nitrogen trophic level effect. Copyright © 2017 John Wiley & Sons, Ltd.

  • the dietary protein paradox and Threonine 15n depletion pyridoxal 5 phosphate enzyme activity as a mechanism for the δ15n trophic level effect
    Rapid Communications in Mass Spectrometry, 2017
    Co-Authors: Benjamin T Fuller, Klaus J Petzke
    Abstract:

    Rationale Nitrogen stable isotope ratios (δ15 N values) are used to reconstruct dietary patterns, but the biochemical mechanism(s) responsible for the diet to tissue trophic level effect and its variability are not fully understood. Here δ15 N amino acid (AA) values and physiological measurements (nitrogen intake, plasma albumin concentrations, liver-reduced glutathione concentrations and leucine oxidation rates) are used to investigate increased dietary protein consumption and oxidative stress (vitamin E deficiency) in rat total plasma protein. Methods Using gas chromatography/combustion/isotope ratio mass spectrometry, the δ15 N values from N-pivaloyl-i-propyl esters of 15 AAs are reported for rats (n = 40) fed casein-based diets with: adequate protein (AP, 13.8%; n = 10), medium protein (MP, 25.7%; n = 10), high protein (HP, 51.3%; n = 10) or HP without vitamin E (HP-E; n = 10) for 18 weeks. Results Between the HP and AP groups, the δ15 NAA values of Threonine (-4.0‰), serine (+1.4‰) and glycine (+1.2‰) display the largest differences and show significant correlations with: nitrogen intake, plasma albumin concentrations, liver-reduced glutathione concentrations and leucine oxidation rates. This indicates increased AA catabolism by the dietary induction of shared common metabolic pathways involving the enzymes Threonine Ammonia-Lyase (EC 4.3.1.19), serine hydroxymethyltransferase (EC 2.1.2.1) and the glycine cleavage system (EC 2.1.2.10). The δ15 NAA values of the HP-E and HP groups were not found to be significantly different. Conclusions The 15 N-depleted results of Threonine are linked to increased activity of Threonine Ammonia-Lyase, and show potential as a possible biomarker for protein intake and/or gluconeogenesis. We hypothesize that the inverse nitrogen equilibrium isotope effects of Schiff base formation, between AAs and pyridoxal-5'-phosphate cofactor enzymes, play a key role in the bioaccumulation and depletion of 15 N in the biomolecules of living organisms and contributes to the variability in the nitrogen trophic level effect. Copyright © 2017 John Wiley & Sons, Ltd.

Lisa Alvarez-cohen - One of the best experts on this subject based on the ideXlab platform.

  • Investigation of Carbon Metabolism in “Dehalococcoides ethenogenes” Strain 195 by Use of Isotopomer and Transcriptomic Analyses
    Journal of bacteriology, 2009
    Co-Authors: Yinjie J. Tang, Wei-qin Zhuang, Stephen H. Zinder, Jay D. Keasling, Lisa Alvarez-cohen
    Abstract:

    Members of the genus “Dehalococcoides” are the only known microorganisms that can completely dechlorinate tetrachloroethene and trichloroethene to the innocuous end product, ethene. This study examines the central metabolism in “Dehalococcoides ethenogenes” strain 195 via 13C-labeled tracer experiments. Supported by the genome annotation and the transcript profile, isotopomer analysis of key metabolites clarifies ambiguities in the genome annotation and identifies an unusual biosynthetic pathway in strain 195. First, the 13C-labeling studies revealed that strain 195 contains complete amino acid biosynthesis pathways, even though current genome annotation suggests that several of these pathways are incomplete. Second, the tricarboxylic acid cycle of strain 195 is confirmed to be branched, and the Wood-Ljungdahl carbon fixation pathway is shown to not be functionally active under our experimental conditions; rather, CO2 is assimilated via two reactions, conversion of acetyl-coenzyme A (acetyl coenzyme A [acetyl-CoA]) to pyruvate catalyzed by pyruvate synthase (DET0724-0727) and pyruvate conversion to oxaloacetate via pyruvate carboxylase (DET0119-0120). Third, the 13C-labeling studies also suggested that isoleucine is synthesized from acetyl-CoA and pyruvate via citramalate synthase (CimA, EC 2.3.1.182), rather than from the common pathway via Threonine Ammonia-Lyase (EC 4.3.1.19). Finally, evidence is presented that strain 195 may contain an undocumented citrate synthase (>95% Re-type stereospecific), i.e., a novel Re-citrate synthase that is apparently different from the one recently reported in Clostridium kluyveri.

  • Investigation of Carbon Metabolism in “Dehalococcoides ethenogenes” Strain 195 by Use of Isotopomer and Transcriptomic Analyses � ‡
    2009
    Co-Authors: Yinjie J. Tang, Wei-qin Zhuang, Stephen H. Zinder, Jay D. Keasling, Lisa Alvarez-cohen
    Abstract:

    Members of the genus “Dehalococcoides ” are the only known microorganisms that can completely dechlorinate tetrachloroethene and trichloroethene to the innocuous end product, ethene. This study examines the central metabolism in “Dehalococcoides ethenogenes ” strain 195 via 13 C-labeled tracer experiments. Supported by the genome annotation and the transcript profile, isotopomer analysis of key metabolites clarifies ambiguities in the genome annotation and identifies an unusual biosynthetic pathway in strain 195. First, the 13 C-labeling studies revealed that strain 195 contains complete amino acid biosynthesis pathways, even though current genome annotation suggests that several of these pathways are incomplete. Second, the tricarboxylic acid cycle of strain 195 is confirmed to be branched, and the Wood-Ljungdahl carbon fixation pathway is shown to not be functionally active under our experimental conditions; rather, CO 2 is assimilated via two reactions, conversion of acetyl-coenzyme A (acetyl coenzyme A [acetyl-CoA]) to pyruvate catalyzed by pyruvate synthase (DET0724-0727) and pyruvate conversion to oxaloacetate via pyruvate carboxylase (DET0119-0120). Third, the 13 C-labeling studies also suggested that isoleucine is synthesized from acetyl-CoA and pyruvate via citramalate synthase (CimA, EC 2.3.1.182), rather than from the common pathway via Threonine Ammonia-Lyase (E

Yinjie J. Tang - One of the best experts on this subject based on the ideXlab platform.

  • Investigation of Carbon Metabolism in “Dehalococcoides ethenogenes” Strain 195 by Use of Isotopomer and Transcriptomic Analyses
    Journal of bacteriology, 2009
    Co-Authors: Yinjie J. Tang, Wei-qin Zhuang, Stephen H. Zinder, Jay D. Keasling, Lisa Alvarez-cohen
    Abstract:

    Members of the genus “Dehalococcoides” are the only known microorganisms that can completely dechlorinate tetrachloroethene and trichloroethene to the innocuous end product, ethene. This study examines the central metabolism in “Dehalococcoides ethenogenes” strain 195 via 13C-labeled tracer experiments. Supported by the genome annotation and the transcript profile, isotopomer analysis of key metabolites clarifies ambiguities in the genome annotation and identifies an unusual biosynthetic pathway in strain 195. First, the 13C-labeling studies revealed that strain 195 contains complete amino acid biosynthesis pathways, even though current genome annotation suggests that several of these pathways are incomplete. Second, the tricarboxylic acid cycle of strain 195 is confirmed to be branched, and the Wood-Ljungdahl carbon fixation pathway is shown to not be functionally active under our experimental conditions; rather, CO2 is assimilated via two reactions, conversion of acetyl-coenzyme A (acetyl coenzyme A [acetyl-CoA]) to pyruvate catalyzed by pyruvate synthase (DET0724-0727) and pyruvate conversion to oxaloacetate via pyruvate carboxylase (DET0119-0120). Third, the 13C-labeling studies also suggested that isoleucine is synthesized from acetyl-CoA and pyruvate via citramalate synthase (CimA, EC 2.3.1.182), rather than from the common pathway via Threonine Ammonia-Lyase (EC 4.3.1.19). Finally, evidence is presented that strain 195 may contain an undocumented citrate synthase (>95% Re-type stereospecific), i.e., a novel Re-citrate synthase that is apparently different from the one recently reported in Clostridium kluyveri.

  • Investigation of Carbon Metabolism in “Dehalococcoides ethenogenes” Strain 195 by Use of Isotopomer and Transcriptomic Analyses � ‡
    2009
    Co-Authors: Yinjie J. Tang, Wei-qin Zhuang, Stephen H. Zinder, Jay D. Keasling, Lisa Alvarez-cohen
    Abstract:

    Members of the genus “Dehalococcoides ” are the only known microorganisms that can completely dechlorinate tetrachloroethene and trichloroethene to the innocuous end product, ethene. This study examines the central metabolism in “Dehalococcoides ethenogenes ” strain 195 via 13 C-labeled tracer experiments. Supported by the genome annotation and the transcript profile, isotopomer analysis of key metabolites clarifies ambiguities in the genome annotation and identifies an unusual biosynthetic pathway in strain 195. First, the 13 C-labeling studies revealed that strain 195 contains complete amino acid biosynthesis pathways, even though current genome annotation suggests that several of these pathways are incomplete. Second, the tricarboxylic acid cycle of strain 195 is confirmed to be branched, and the Wood-Ljungdahl carbon fixation pathway is shown to not be functionally active under our experimental conditions; rather, CO 2 is assimilated via two reactions, conversion of acetyl-coenzyme A (acetyl coenzyme A [acetyl-CoA]) to pyruvate catalyzed by pyruvate synthase (DET0724-0727) and pyruvate conversion to oxaloacetate via pyruvate carboxylase (DET0119-0120). Third, the 13 C-labeling studies also suggested that isoleucine is synthesized from acetyl-CoA and pyruvate via citramalate synthase (CimA, EC 2.3.1.182), rather than from the common pathway via Threonine Ammonia-Lyase (E

Jay D. Keasling - One of the best experts on this subject based on the ideXlab platform.

  • Investigation of Carbon Metabolism in “Dehalococcoides ethenogenes” Strain 195 by Use of Isotopomer and Transcriptomic Analyses
    Journal of bacteriology, 2009
    Co-Authors: Yinjie J. Tang, Wei-qin Zhuang, Stephen H. Zinder, Jay D. Keasling, Lisa Alvarez-cohen
    Abstract:

    Members of the genus “Dehalococcoides” are the only known microorganisms that can completely dechlorinate tetrachloroethene and trichloroethene to the innocuous end product, ethene. This study examines the central metabolism in “Dehalococcoides ethenogenes” strain 195 via 13C-labeled tracer experiments. Supported by the genome annotation and the transcript profile, isotopomer analysis of key metabolites clarifies ambiguities in the genome annotation and identifies an unusual biosynthetic pathway in strain 195. First, the 13C-labeling studies revealed that strain 195 contains complete amino acid biosynthesis pathways, even though current genome annotation suggests that several of these pathways are incomplete. Second, the tricarboxylic acid cycle of strain 195 is confirmed to be branched, and the Wood-Ljungdahl carbon fixation pathway is shown to not be functionally active under our experimental conditions; rather, CO2 is assimilated via two reactions, conversion of acetyl-coenzyme A (acetyl coenzyme A [acetyl-CoA]) to pyruvate catalyzed by pyruvate synthase (DET0724-0727) and pyruvate conversion to oxaloacetate via pyruvate carboxylase (DET0119-0120). Third, the 13C-labeling studies also suggested that isoleucine is synthesized from acetyl-CoA and pyruvate via citramalate synthase (CimA, EC 2.3.1.182), rather than from the common pathway via Threonine Ammonia-Lyase (EC 4.3.1.19). Finally, evidence is presented that strain 195 may contain an undocumented citrate synthase (>95% Re-type stereospecific), i.e., a novel Re-citrate synthase that is apparently different from the one recently reported in Clostridium kluyveri.

  • Investigation of Carbon Metabolism in “Dehalococcoides ethenogenes” Strain 195 by Use of Isotopomer and Transcriptomic Analyses � ‡
    2009
    Co-Authors: Yinjie J. Tang, Wei-qin Zhuang, Stephen H. Zinder, Jay D. Keasling, Lisa Alvarez-cohen
    Abstract:

    Members of the genus “Dehalococcoides ” are the only known microorganisms that can completely dechlorinate tetrachloroethene and trichloroethene to the innocuous end product, ethene. This study examines the central metabolism in “Dehalococcoides ethenogenes ” strain 195 via 13 C-labeled tracer experiments. Supported by the genome annotation and the transcript profile, isotopomer analysis of key metabolites clarifies ambiguities in the genome annotation and identifies an unusual biosynthetic pathway in strain 195. First, the 13 C-labeling studies revealed that strain 195 contains complete amino acid biosynthesis pathways, even though current genome annotation suggests that several of these pathways are incomplete. Second, the tricarboxylic acid cycle of strain 195 is confirmed to be branched, and the Wood-Ljungdahl carbon fixation pathway is shown to not be functionally active under our experimental conditions; rather, CO 2 is assimilated via two reactions, conversion of acetyl-coenzyme A (acetyl coenzyme A [acetyl-CoA]) to pyruvate catalyzed by pyruvate synthase (DET0724-0727) and pyruvate conversion to oxaloacetate via pyruvate carboxylase (DET0119-0120). Third, the 13 C-labeling studies also suggested that isoleucine is synthesized from acetyl-CoA and pyruvate via citramalate synthase (CimA, EC 2.3.1.182), rather than from the common pathway via Threonine Ammonia-Lyase (E