Quesada-Soriano I, García-Maroto F, García-Fuentes L. Kinetic study on the irreversible thermal denaturation of Schistosoma japonicum glutathione s-transferase.
BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006;
1764:979-84. [PMID:
16630751 DOI:
10.1016/j.bbapap.2006.03.002]
[Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 03/03/2006] [Accepted: 03/09/2006] [Indexed: 10/24/2022]
Abstract
The thermal unfolding pathway of the Schistosoma japonicum glutathione S-transferase (Sj26GST) was previously interpreted by applying equilibrium thermodynamics and a reversible two-state model (Kaplan et al., (1997) Protein Science, 6, 399-406), though weak support for this interpretation was provided. In our study, thermal denaturation of Sj26GST has been re-examined by differential scanning calorimetry in the pH range of 6.5-8.5 and in the presence of the substrate and S-hexylglutathione. Calorimetric traces were found to be irreversible and highly scan-rate dependent. Thermogram shapes, as well as their scan-rate dependence, can be globally explained by assuming that thermal denaturation takes place according to one irreversible step described by a first-order kinetic constant that changes with temperature, as given by an Arrhenius equation. On the basis of this model, values for the rate constant as a function of temperature and the activation energy have been determined. Data also indicate that binding of GSH or S-hexylglutathione just exert a very little stabilising effect on the dimeric structure of the molecule.
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