Interactions between trypsin and its peptidic inhibitors studied by isothermal titration calorimetry (ITC)

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• 作者：Dawid Dębowski ; Dariusz Wyrzykowski…
• 关键词：Isothermal titration calorimetry ; Serine protease inhibitors ; Sunflower trypsin inhibitor 1 ; Reaction stoichiometry
• 刊名：Journal of Thermal Analysis and Calorimetry
• 出版年：2016
• 出版时间：January 2016
• 年：2016
• 卷：123
• 期：1
• 页码：807-812
• 全文大小：513 KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Sciences
  Polymer Sciences
  Physical Chemistry
  Inorganic Chemistry
  Measurement Science and Instrumentation
  
• 出版者：Akad茅miai Kiad贸, co-published with Springer Science+Business Media B.V., Formerly Kluwer Academic
• ISSN：1572-8943

文摘

Isothermal titration calorimetry (ITC) technique was used to study the interactions of trypsin with bicyclic sunflower-derived trypsin inhibitor (SFTI-1) as well as with its new monocyclic (with disulphide bridge only) analogues (C₃H₅O)–SFTI-1 and (C₈H₁₅O)–SFTI-1. ITC measurements were run in 50 mM buffer solution of HEPES or Tricine of pH 8, containing 20 mM CaCl₂ at 298.15 K. Based on calorimetric data, the equilibrium constants for the inhibitor–enzyme-binding processes, K, the binding stoichiometry, N (inhibitor-to-enzyme molar ratio), as well as thermodynamic parameters (ΔG, ΔH, ΔS) for the reactions were determined. The study revealed that the stoichiometry of the resulting complexes equals 1:1. The negative binding enthalpy (Δ_ITC H) and favourable entropy factor (TΔ_ITC S) suggest an important contribution of hydrogen bonding as well as hydrophobic interactions to the inhibitor–enzyme affinity. Furthermore, the relationship between the modification of the peptide structure, the experimental conditions and the thermodynamic parameters has been discussed.