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Udo Wendel - One of the best experts on this subject based on the ideXlab platform.
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Significance of L-Alloisoleucine in Plasma for Diagnosis of Maple Syrup Urine Disease
2015Co-Authors: Peter Schadewaldt, Hans-werner Hammen, Annette Bodner-leidecker, Udo WendelAbstract:leucine, which is derived from L-isoleucine in vivo, for diagnosis of maple syrup urine disease (MSUD) was examined. Methods: Branched-chain L-amino acids were measured by automatic amino acid analysis. Results: Alloisoleucine reference values in plasma were established in healthy adults [1.9 6 0.6 mmol/L (mean 6 SD); n 5 35], children 3–11 years (1.6 6 0.4 mmol/L; n 5 17), and infants <3 years (1.3 6 0.5 mmol/L; n 5 37). The effect of dietary isoleucine was assessed in oral loading tests. In controls receiving 38 mmol (n 5 6; low dose) and 1527 mmol (n 5 3; high dose) of L-isoleucine per kilo-gram of body weight, peak increases of plasma isoleu-cine were 78 6 24 and 1763 6 133 mmol/L, respectively; the peak increase of Alloisoleucine, however, was neg
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Formation of L-Alloisoleucine In Vivo : An L-[^13C]Isoleucine Study in Man
Pediatric Research, 2000Co-Authors: Peter Schadewaldt, Hans-werner Hammen, Annette Bodner-leidecker, Udo WendelAbstract:L-Alloisoleucine (2 S , 3 R ), a diastereomer of L-isoleucine (2 S , 3 S ), is a normal constituent of human plasma. Considerable amounts accumulate in maple syrup urine disease, in which the branched-chain 2-oxo acid dehydrogenase step is impaired. The mechanism of L-Alloisoleucine formation, however, is unclear. We addressed this issue by performing oral L-[1-^13C]isoleucine loading (38 μmol/kg body wt, 50% 1-^13C) in overnight-fasted healthy subjects ( n = 4) and measuring the 3-h kinetics of ^13C-label incorporation into L-isoleucine plasma metabolites. Compared with L-isoleucine, the time course of ^13C-enrichment in the related 2-oxo acid, S -3-methyl-2-oxopentanoate, was only slightly delayed. Peak values, amounting to 18 ± 4 and 17 ± 3 mol percent excess, respectively, were reached within 35 and 45 min, respectively. The kinetics of ^13C-enrichment in S - and R -3-methyl-2-oxopentanoate enantiomorphs were similar and linearly correlated ( p ≪ 0.001). In L-Alloisoleucine, however, ^13C-label accumulated only gradually and in minor amounts. Our results indicate that R -3-methyl-2-oxopentanoate is an immediate and inevitable byproduct of L-isoleucine transamination and further suggest that Alloisoleucine is primarily formed via retransamination of 3-methyl-2-oxopenanoate in vivo .
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Formation of L-Alloisoleucine in vivo: an L-[13C]isoleucine study in man.
Pediatric research, 2000Co-Authors: Peter Schadewaldt, Hans-werner Hammen, Annette Bodner-leidecker, Udo WendelAbstract:L-Alloisoleucine (2 S, 3 R), a diastereomer of L-isoleucine (2 S, 3 S), is a normal constituent of human plasma. Considerable amounts accumulate in maple syrup urine disease, in which the branched-chain 2-oxo acid dehydrogenase step is impaired. The mechanism of L-Alloisoleucine formation, however, is unclear. We addressed this issue by performing oral L-[1-13C]isoleucine loading (38 μmol/kg body wt, 50% 1-13C) in overnight-fasted healthy subjects (n = 4) and measuring the 3-h kinetics of 13C-label incorporation into L-isoleucine plasma metabolites. Compared with L-isoleucine, the time course of 13C-enrichment in the related 2-oxo acid, S-3-methyl-2-oxopentanoate, was only slightly delayed. Peak values, amounting to 18 ± 4 and 17 ± 3 mol percent excess, respectively, were reached within 35 and 45 min, respectively. The kinetics of 13C-enrichment in S- and R-3-methyl-2-oxopentanoate enantiomorphs were similar and linearly correlated (p 0.001). In L-Alloisoleucine, however, 13C-label accumulated only gradually and in minor amounts. Our results indicate that R-3-methyl-2-oxopentanoate is an immediate and inevitable byproduct of L-isoleucine transamination and further suggest that Alloisoleucine is primarily formed via retransamination of 3-methyl-2-oxopenanoate in vivo.
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Significance of l-Alloisoleucine in Plasma for Diagnosis of Maple Syrup Urine Disease
Clinical chemistry, 1999Co-Authors: Peter Schadewaldt, Hans-werner Hammen, Annette Bodner-leidecker, Udo WendelAbstract:Background: The significance of plasma l-Alloisoleucine, which is derived from l-isoleucine in vivo, for diagnosis of maple syrup urine disease (MSUD) was examined. Methods: Branched-chain l-amino acids were measured by automatic amino acid analysis. Results: Alloisoleucine reference values in plasma were established in healthy adults [1.9 ± 0.6 μmol/L (mean ± SD); n = 35], children 3–11 years (1.6 ± 0.4 μmol/L; n = 17), and infants 5 μmol/L in all samples taken for establishment of diagnosis and in 94% of the samples taken for treatment control (n = 624). With the other branched-chain amino acids, the frequency of diagnostically significant increases was Conclusions: The present findings indicate that plasma l-Alloisoleucine above the cutoff value of 5 μmol/L is the most specific and most sensitive diagnostic marker for all forms of MSUD.
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Determination of (S)- and (R)-2-oxo-3-methylvaleric acid in plasma of patients with maple syrup urine disease.
Clinica chimica acta; international journal of clinical chemistry, 1992Co-Authors: Udo Wendel, Peter Schadewaldt, Gertrud Even, U. Langenbeck, Werner HummelAbstract:Abstract An enzymatic method for the separate measurement of both chiral 2-oxo-3-methylvaleric acid (OMV) compounds, (S)- and (R)-OMV, by NADH-dependent enantioselective animation using leucine dehydrogenase in the presence of a NADH regenerating system is described. This method allows the quantitative determination of all branched-chain 2-oxo acids, simultaneously. In plasma samples from classical maple syrup urine disease patients under therapy the average (R)-OMV/(S)-OMV ratio was 0.35 and great differences in the transamination equilibria of the diastereomeric branched-chain amino acids l -isoleucine and l -Alloisoleucine were demonstrated.
Peter Schadewaldt - One of the best experts on this subject based on the ideXlab platform.
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Significance of L-Alloisoleucine in Plasma for Diagnosis of Maple Syrup Urine Disease
2015Co-Authors: Peter Schadewaldt, Hans-werner Hammen, Annette Bodner-leidecker, Udo WendelAbstract:leucine, which is derived from L-isoleucine in vivo, for diagnosis of maple syrup urine disease (MSUD) was examined. Methods: Branched-chain L-amino acids were measured by automatic amino acid analysis. Results: Alloisoleucine reference values in plasma were established in healthy adults [1.9 6 0.6 mmol/L (mean 6 SD); n 5 35], children 3–11 years (1.6 6 0.4 mmol/L; n 5 17), and infants <3 years (1.3 6 0.5 mmol/L; n 5 37). The effect of dietary isoleucine was assessed in oral loading tests. In controls receiving 38 mmol (n 5 6; low dose) and 1527 mmol (n 5 3; high dose) of L-isoleucine per kilo-gram of body weight, peak increases of plasma isoleu-cine were 78 6 24 and 1763 6 133 mmol/L, respectively; the peak increase of Alloisoleucine, however, was neg
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Formation of L-Alloisoleucine In Vivo : An L-[^13C]Isoleucine Study in Man
Pediatric Research, 2000Co-Authors: Peter Schadewaldt, Hans-werner Hammen, Annette Bodner-leidecker, Udo WendelAbstract:L-Alloisoleucine (2 S , 3 R ), a diastereomer of L-isoleucine (2 S , 3 S ), is a normal constituent of human plasma. Considerable amounts accumulate in maple syrup urine disease, in which the branched-chain 2-oxo acid dehydrogenase step is impaired. The mechanism of L-Alloisoleucine formation, however, is unclear. We addressed this issue by performing oral L-[1-^13C]isoleucine loading (38 μmol/kg body wt, 50% 1-^13C) in overnight-fasted healthy subjects ( n = 4) and measuring the 3-h kinetics of ^13C-label incorporation into L-isoleucine plasma metabolites. Compared with L-isoleucine, the time course of ^13C-enrichment in the related 2-oxo acid, S -3-methyl-2-oxopentanoate, was only slightly delayed. Peak values, amounting to 18 ± 4 and 17 ± 3 mol percent excess, respectively, were reached within 35 and 45 min, respectively. The kinetics of ^13C-enrichment in S - and R -3-methyl-2-oxopentanoate enantiomorphs were similar and linearly correlated ( p ≪ 0.001). In L-Alloisoleucine, however, ^13C-label accumulated only gradually and in minor amounts. Our results indicate that R -3-methyl-2-oxopentanoate is an immediate and inevitable byproduct of L-isoleucine transamination and further suggest that Alloisoleucine is primarily formed via retransamination of 3-methyl-2-oxopenanoate in vivo .
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Formation of L-Alloisoleucine in vivo: an L-[13C]isoleucine study in man.
Pediatric research, 2000Co-Authors: Peter Schadewaldt, Hans-werner Hammen, Annette Bodner-leidecker, Udo WendelAbstract:L-Alloisoleucine (2 S, 3 R), a diastereomer of L-isoleucine (2 S, 3 S), is a normal constituent of human plasma. Considerable amounts accumulate in maple syrup urine disease, in which the branched-chain 2-oxo acid dehydrogenase step is impaired. The mechanism of L-Alloisoleucine formation, however, is unclear. We addressed this issue by performing oral L-[1-13C]isoleucine loading (38 μmol/kg body wt, 50% 1-13C) in overnight-fasted healthy subjects (n = 4) and measuring the 3-h kinetics of 13C-label incorporation into L-isoleucine plasma metabolites. Compared with L-isoleucine, the time course of 13C-enrichment in the related 2-oxo acid, S-3-methyl-2-oxopentanoate, was only slightly delayed. Peak values, amounting to 18 ± 4 and 17 ± 3 mol percent excess, respectively, were reached within 35 and 45 min, respectively. The kinetics of 13C-enrichment in S- and R-3-methyl-2-oxopentanoate enantiomorphs were similar and linearly correlated (p 0.001). In L-Alloisoleucine, however, 13C-label accumulated only gradually and in minor amounts. Our results indicate that R-3-methyl-2-oxopentanoate is an immediate and inevitable byproduct of L-isoleucine transamination and further suggest that Alloisoleucine is primarily formed via retransamination of 3-methyl-2-oxopenanoate in vivo.
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Significance of l-Alloisoleucine in Plasma for Diagnosis of Maple Syrup Urine Disease
Clinical chemistry, 1999Co-Authors: Peter Schadewaldt, Hans-werner Hammen, Annette Bodner-leidecker, Udo WendelAbstract:Background: The significance of plasma l-Alloisoleucine, which is derived from l-isoleucine in vivo, for diagnosis of maple syrup urine disease (MSUD) was examined. Methods: Branched-chain l-amino acids were measured by automatic amino acid analysis. Results: Alloisoleucine reference values in plasma were established in healthy adults [1.9 ± 0.6 μmol/L (mean ± SD); n = 35], children 3–11 years (1.6 ± 0.4 μmol/L; n = 17), and infants 5 μmol/L in all samples taken for establishment of diagnosis and in 94% of the samples taken for treatment control (n = 624). With the other branched-chain amino acids, the frequency of diagnostically significant increases was Conclusions: The present findings indicate that plasma l-Alloisoleucine above the cutoff value of 5 μmol/L is the most specific and most sensitive diagnostic marker for all forms of MSUD.
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Determination of (S)- and (R)-2-oxo-3-methylvaleric acid in plasma of patients with maple syrup urine disease.
Clinica chimica acta; international journal of clinical chemistry, 1992Co-Authors: Udo Wendel, Peter Schadewaldt, Gertrud Even, U. Langenbeck, Werner HummelAbstract:Abstract An enzymatic method for the separate measurement of both chiral 2-oxo-3-methylvaleric acid (OMV) compounds, (S)- and (R)-OMV, by NADH-dependent enantioselective animation using leucine dehydrogenase in the presence of a NADH regenerating system is described. This method allows the quantitative determination of all branched-chain 2-oxo acids, simultaneously. In plasma samples from classical maple syrup urine disease patients under therapy the average (R)-OMV/(S)-OMV ratio was 0.35 and great differences in the transamination equilibria of the diastereomeric branched-chain amino acids l -isoleucine and l -Alloisoleucine were demonstrated.
Marcus J. Miller - One of the best experts on this subject based on the ideXlab platform.
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Rapid quantification of underivatized Alloisoleucine and argininosuccinate using mixed-mode chromatography with tandem mass spectrometry
Journal of chromatography. B Analytical technologies in the biomedical and life sciences, 2019Co-Authors: Chandler Griffin, Zineb Ammous, Gail H. Vance, Brett H. Graham, Marcus J. MillerAbstract:Abstract Plasma elevations of the amino acids Alloisoleucine and argininosuccinic acid (ASA) are pathognomonic for maple syrup urine disease and argininosuccinate lyase deficiency, respectively. Reliable detection of these biomarkers is typically achieved using methods with tedious sample preparations or long chromatographic separations, and many published amino acid assays report poor specificity and/or sensitivity for one or both of these compounds. This report describes a novel liquid chromatography tandem mass spectrometry (LC-MS/MS) method that provides rapid quantification of Alloisoleucine and ASA in human plasma. The basis of this method is a mixed-mode solid phase separation that achieves baseline resolution of Alloisoleucine from isobaric interferents without the use of derivatization or ion pairing agents. The inject-to-inject time is 6 min including elution, column washing and re-equilibration. Validation studies demonstrate excellent limits of quantification (1 μmol/L), linearity (r = 0.999 from 1 to 250 μmol/L), accuracy (bias = −3.8% and −10.1%), and inter-assay imprecision (CV
Argante Bozzi - One of the best experts on this subject based on the ideXlab platform.
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Membrane interaction and antibacterial properties of two mildly cationic peptide diastereomers, bombinins H2 and H4, isolated from Bombina skin
European biophysics journal : EBJ, 2011Co-Authors: Cristina Coccia, Andrea Rinaldi, Vincenzo Luca, Donatella Barra, Argante Bozzi, Antonio Di Giulio, Enno C. I. Veerman, Maria Luisa MangoniAbstract:Bombinins H are mildly cationic antimicrobial peptides isolated from the skin of the anuran genus Bombina, the fire-bellied toad. Some members of this peptide family coexist in skin secretions as diastereomers in which a single d-amino acid (Alloisoleucine or leucine) is incorporated as a result of the post-translational modification of the respective gene-encoded l-amino acid. Here we report on the antimicrobial properties and membrane interactions of bombinins H2 and H4. The latter differs from H2 by the presence of a d-Alloisoleucine at the second N-terminal position. Specifically, we have evaluated the antimicrobial activity of H2 and H4 against a large panel of reference and clinical isolates of Gram-negative and Gram-positive bacteria; performed membrane permeation assays on both intact cells and model membranes (lipid monolayers and liposomes) mimicking the composition of the plasma membrane of Gram-negative/positive bacteria; used biochemical tools, such as trypsin-encapsulated liposomes and capillary electrophoresis, to monitor the peptides’ ability to translocate through the membrane of liposomes mimicking Escherichia coli inner membrane. The results revealed interesting relationships between the presence of a single d-amino acid in the sequence of an antimicrobial peptide and its target microbial cell selectivity/membrane-perturbing activity.
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Folding propensity and biological activity of peptides: the effect of a single stereochemical isomerization on the conformational properties of bombinins in aqueous solution.
Biopolymers, 2008Co-Authors: Argante Bozzi, Maria Luisa Mangoni, Andrea Rinaldi, Giuseppina Mignogna, Massimiliano AschiAbstract:Folding propensities of bombinins H2 and H4, two members of amphibian bombinins H, a family of 17-20 residue alpha-helical peptides, have been investigated by means of circular dichroism (CD) measurements and molecular dynamics (MD) simulations. The two peptides, with primary structure IIGPVLGLVGSALGGLLKKI-NH2 and differing only for the configuration of the second aminoacid (an L-isoleucine in H2 and a D-Alloisoleucine in H4) behave rather differently in solution. In particular both CD measurements and MD simulations indicate that bombinin H2 shows a markedly higher tendency to fold. From a careful inspection of MD trajectories it emerges that the stereochemical isomerization mutation of residue 2 to D-Alloisoleucine in H4 peptide, drastically decreases its ability to form intrapeptide contacts. MD simulations also indicate that the conformational sampling in both systems derives from a subtle combination of energetic and entropic effects both involving the peptide itself and the solvent. The present results have been finally paralleled with preliminary information on bombinins H2 and H4 biological activity, i.e. interaction with membrane, supporting the hypothesis of an "already folded" conformation in water rather than interfacial folding tenet.
Massimiliano Aschi - One of the best experts on this subject based on the ideXlab platform.
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Folding propensity and biological activity of peptides: the effect of a single stereochemical isomerization on the conformational properties of bombinins in aqueous solution.
Biopolymers, 2008Co-Authors: Argante Bozzi, Maria Luisa Mangoni, Andrea Rinaldi, Giuseppina Mignogna, Massimiliano AschiAbstract:Folding propensities of bombinins H2 and H4, two members of amphibian bombinins H, a family of 17-20 residue alpha-helical peptides, have been investigated by means of circular dichroism (CD) measurements and molecular dynamics (MD) simulations. The two peptides, with primary structure IIGPVLGLVGSALGGLLKKI-NH2 and differing only for the configuration of the second aminoacid (an L-isoleucine in H2 and a D-Alloisoleucine in H4) behave rather differently in solution. In particular both CD measurements and MD simulations indicate that bombinin H2 shows a markedly higher tendency to fold. From a careful inspection of MD trajectories it emerges that the stereochemical isomerization mutation of residue 2 to D-Alloisoleucine in H4 peptide, drastically decreases its ability to form intrapeptide contacts. MD simulations also indicate that the conformational sampling in both systems derives from a subtle combination of energetic and entropic effects both involving the peptide itself and the solvent. The present results have been finally paralleled with preliminary information on bombinins H2 and H4 biological activity, i.e. interaction with membrane, supporting the hypothesis of an "already folded" conformation in water rather than interfacial folding tenet.