- Novel peptide with a specific calcium-binding capacity from whey protein hydrolysate and the possible chelating mode
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A novel peptide with a specific calcium-binding capacity was isolated from whey protein hydrolysates. The isolation procedures included diethylaminoethyl (DEAE) anion-exchange chromatography, Sephadex G-25 gel filtration, and reversed-phase high-performance liquid chromatography (HPLC). A peptide with a molecular mass of 237.99 Da was identified by liquid chromatography-electrospray ionization/mass spectrometry (LC-ESI/MS), and its amino acid sequence was confirmed to be Gly-Tyr. The calcium-binding capacity of Gly-Tyr reached 75.38 μg/mg, increasing by 122% when compared to the hydrolysate complex. The chelating interaction mode between the Gly-Tyr and calcium ion was investigated, indicating that the major binding sites included the oxygen atom of the carbonyl group and nitrogen of the amino or imino group. The folding and structural modification of the peptide arose along with the addition of the calcium ion. The profile of 1H nuclear magnetic resonance (NMR) spectroscopy demonstrated that the electron cloud density around the hydrogen nucleus in the peptide changed was caused by the calcium ion. The results of ζ potential showed that the Gly-Tyr-Ca chelate was a neutral molecule in which the calcium ion was surrounded by the specific binding sites of the peptide. Moreover, thermogravimetry-differential scanning calorimetry (TG-DSC) and calcium-releasing assay revealed that the Gly-Tyr-Ca chelate exerted excellent thermal stability and solubility in both acidic and basic conditions, which were beneficial to calcium absorption in the gastrointestinal tract of the human body and, therefore, improved its bioavailability. These findings further the progress in the research of whey protein, suggesting the potential in making peptide-calcium chelate as a dietary supplement.
- Zhao, Lina,Huang, Qimin,Huang, Shunli,Lin, Jiaping,Wang, Shaoyun,Huang, Yifan,Hong, Jing,Rao, Pingfan
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- N5-Methylasparagine and Asparagine as Nucleophiles in Peptides: Main-Chain vs Side-Chain Amide Cleavage
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The chemistry of peptides containing N5-methylasparagine (NMA) was investigated by incubating the synthetic peptides Ile-Ala-Pro-Gly-Asn-Gly-Tyr and Ile-Ala-Pro-Gly-Gly-NMA-Gly-Tyr at 60 deg C in 0.1 M NaPO4, pH 7.4, to assay for peptide deamidation.The Asn-Gly octapeptide deamidates to Ile-Ala-Pro-Gly-Gly-isoAsp/Asp-Gly-Tyr with a half-life of 2.17 h and activation energy of 18.6 kcal/mol.The NMA-Gly octapeptide partitions between main-chain cleavage and side-chain deamidation in 2.7:1 ratio.Analysis of products diagnostic for each of these NMA peptide reactions yields indistinguishable activation energies for each pathway: 22.6 kcal/mol.The half-life for NMA side-chain deamidation is 98 h, commensurate with a 2.5 kcal/mol difference in activation free energies for deamidation at Asn and NMA sites.These results indicate that methylation provides a substantial (45-fold) stabilization against intramolecular C-N cleavage.The identical activation energy for the alternative pathways of NMA peptide reactivity suggests the differences in the rates may be due to the preexponential portion of the rate equation reflecting small differences in ΔS(excit.).Molecular mechanics studies were performed to account for these patterns.The computational studies disclose 3-fold more conformers in the Boltzmann population for the tetrahedral intermediate leading toward main-chain cleavage.This result supports the hypothesis that the 2.7-fold differences in NMA peptide partitioning rates is attributable to differences in ΔS(excit.).
- Klotz, Alan V.,Thomas, Beth Ann
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- Identification of novel L-amino acid α-ligases through hidden markov model-based profile analysis
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L-Amino acid α-ligase (Lal), catalyzing the formation of α-dipeptides from unprotected l-amino acids in an ATP-dependent manner, is used in cost-effective fermentative production of dipeptides. We searched for novel Lals by in silico screening using Hidden Markov Model-based profile analysis, and identified five novel Lals that showed low similarity and different substrate specificity from known Lals.
- Senoo, Akihiro,Tabata, Kazuhiko,Yonetani, Yoshiyuki,Yagasaki, Makoto
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p. 415 - 418
(2010/09/30)
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- Process for producing N-glycyltyrosine and its crystal structure
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Provided is a process for efficiently producing N-glycyltyrosine of high purity represented by the following formula: a salt thereof, or a solvate thereof, which comprises adding dropwise to an aqueous suspension of tyrosine or a salt thereof 2 equivalents or more of a haloacetyl halide and an aqueous solution of an inorganic base simultaneously in the presence or absence of an organic solvent, and subjecting the resulting N-haloacetyltyrosine to a reaction with an ammonium ion. Also provided are N-glycyl-L-tyrosine dehydrate having the crystal structures showing specific diffraction patterns in X-ray powder diffraction and processes for producing the same which are characterized by comprising crystallizing the dihydrate from an ethanol-water mixed solvent or water.
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- Increased stability of peptidesulfonamide peptidomimetics towards protease catalyzed degradation
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Replacement of amide bonds in peptides by sulfonamide moieties resulted in peptidosulfonamides with an increased stability towards protease catalyzed degradation. In addition to protection of the protease cleavage site, it was found that introduction of a sulfonamide also influenced the stability of adjacent amide bonds. Copyright (C) 1999 Elsevier Science Ltd.
- De Bont, Dries B.A.,Sliedregt-Bol, Karen M.,Hofmeyer, Lovina J. F.,Liskamp, Rob M. J.
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p. 1043 - 1047
(2007/10/03)
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- High-performance liquid chromatographic analysis of pulmonary metabolites of Leu- and Met-enkephalins in isolated perfused rat lung
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A high-performance liquid radiochromatographic analytical system has been developed which allows the determination of [3H]Leu-enkephalin, [3H]Met-enkephalin and their potential metabolites [3H]TyrGlyGlyPhe, [3H]TyrGlyGly, [3H]TyrGly and [3H]tyrosine. Using this procedure, the biotransformation of each of the above enkephalins after 20 min of recirculating transit through isolated perfused rat lungs resulted in the formation of two major metabolites: tyrosine and TyrGlyGly in each case. The results indicate that significant metabolism of enkephalins may occur in the pulmonary circulation.
- Crooks,Krechniak,Olson,Gillespie
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p. 1010 - 1012
(2007/10/02)
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