Pseudoirreversible slow-binding inhibition of trypanothione reductase by a protein-protein interaction disruptor.
Br J Pharmacol
; 177(22): 5163-5176, 2020 11.
Article
de En
| MEDLINE
| ID: mdl-32888319
ABSTRACT
BACKGROUND AND PURPOSE:
Peptide P4 was described as a dimerization disruptor of trypanothione reductase (TryR), a homodimeric enzyme essential for survival of trypanosomatids. Determination of the true inhibitory constant (Ki ) for P4 was not achieved because reaction rates continuously decreased with time, even when substrate concentration was kept constant. The aim of this study was to find a suitable kinetic model that could allow characterization of the complex pattern of TryR inhibition caused by P4. EXPERIMENTALAPPROACH:
After showing the slow-binding and pseudoirreversible activity of P4 against Leishmania infantum trypanothione reductase (Li-TryR), analysis of the curvatures of the reaction progress curves at different inhibitor concentrations allowed us to define the apparent inhibitory constants (Kiapp ) at five different substrate concentrations. Analysis of the changes in Kiapp values allowed precise definition of the type of inhibition. KEYRESULTS:
Li-TryR inhibition by P4 requires two sequential steps that involve rapid generation of a reversible enzyme-inhibitor complex followed by a pseudoirreversible slow inactivation of the enzyme. Recovery of enzyme activity after inhibitor dissociation is barely detectable. P4 is a non-competitive pseudoirreversible inhibitor of Li- TryR that displays an overall inhibition constant (Ki* ) smaller than 0.02 µM. CONCLUSION AND IMPLICATIONS Li-TryRdimer disruption by peptide P4 is a pseudoirreversible time-dependent process which is non-competitive with respect to the oxidized trypanothione (TS2 ) substrate. Therefore, unlike reversible Li-TryR competitive inhibitors, enzyme inhibition by P4 is not affected by the TS2 accumulation observed during oxidant processes such as the oxidative burst in host macrophages.Mots clés
Texte intégral:
1
Collection:
01-internacional
Base de données:
MEDLINE
Sujet principal:
Leishmania infantum
/
NADH, NADPH oxidoreductases
Langue:
En
Journal:
Br J Pharmacol
Année:
2020
Type de document:
Article
Pays d'affiliation:
Espagne