Abstract
The effect of Ile-Val concentration (up to 2.0 M) on the thermodynamic parameters for the binding of the porcine pancreatic secretory trypsin inhibitor (Kazal inhibitor) to trypsinogen has been investigated at pH 5.5 between 7°C and 42°C. Thermodynamic parameters for Kazal inhibitor binding to the Ile-Val:zymogen adduct are more favorable than those observed for inhibitor association to the free proenzyme, but less so than those reported for β-trypsin: Kazal inhibitor adduct formation (even under saturating dipeptide concentrations), suggesting that the effector dipeptide does not induce a complete rigidification of the proenzyme's activation domain. Considering the dependence of the association equilibrium constant for Kazal inhibitor binding to trypsinogen from Ile-Val concentration, thermodynamic parameters for the effector dipeptide binding to the free proenzyme and to its binary complex with Kazal inhibitor have been obtained. Differences in affinity for Ile-Val binding to the free zymogen and its binary complexes with inhibitors and substrates are indicative of the presence of different activation levels of the proenzyme, none of them exactly coincident with that of β-trypsin. Such different discrete states should correspond to those involved in the zymogen-to-active-enzyme transition which should not be considered as an all-or-nothing process, but as a multistep event.
Original language | English |
---|---|
Pages (from-to) | 378-382 |
Number of pages | 5 |
Journal | Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular |
Volume | 832 |
Issue number | 3 |
DOIs | |
Publication status | Published - Dec 20 1985 |
Keywords
- (Bovine, Porcine pancreas)
- Ile-Val effector dipeptide
- Kazal inhibitor
- Thermodynamics
- Trypsin inhibitor binding thermodynamics
- Trypsinogen activation
ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Molecular Biology
- Structural Biology