Salt influence on glutathione—Schistosoma japonicum glutathione S-transferase binding

Yassin, Zeyad; Clemente-Jimenez, M.Jose; Téllez-Sanz, Ramiro; Garcı́a-Fuentes, Luis

doi:10.1016/s0141-8130(02)00077-6

Cited by 5 publications

(1 citation statement)

References 31 publications

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“…These results suggest that electrostatic interactions are not significant in ensuring a functioning the active site region, in contrast with the Sigma/Theta GST classes (42). A similar insensitivity to ionic strength in the binding of substrate was also found in Sj26GST (43).…”

Section: Figmentioning

confidence: 61%

Thermodynamic Description of the Effect of the Mutation Y49F on Human Glutathione Transferase P1-1 in Binding with Glutathione and the Inhibitor S-Hexylglutathione

Ortiz‐Salmerón

Nuccetelli

Oakley

et al. 2003

Journal of Biological Chemistry

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The thermodynamics of binding of both the substrate glutathione (GSH) and the competitive inhibitor S-hexylglutathione to the mutant Y49F of human glutathione S-transferase (hGST P1-1), a key residue at the dimer interface, has been investigated by isothermal titration calorimetry and fluorescence spectroscopy. Calorimetric measurements indicated that the binding of these ligands to both the Y49F mutant and wild-type enzyme is enthalpically favorable and entropically unfavorable over the temperature range studied. The affinity of these ligands for the Y49F mutant is lower than those for the wild-type enzyme due mainly to an entropy change. Therefore, the thermodynamic effect of this mutation is to decrease the entropy loss due to binding. Calorimetric titrations in several buffers with different ionization heat amounts indicate a release of protons when the mutant binds GSH, whereas protons are taken up in binding S-hexylglutathione at pH 6.5. This suggests that the thiol group of GSH releases protons to buffer media during binding and a group with low pK a (such as Asp 98 ) is responsible for the uptake of protons. The temperature dependence of the free energy of binding, ⌬G 0 , is weak because of the enthalpy-entropy compensation caused by a large heat capacity change. The heat capacity change is ؊199.5 ؎ 26.9 cal K ؊1 mol ؊1 for GSH binding and ؊333.6 ؎ 28.8 cal K ؊1 mol ؊1 for S-hexylglutathione binding. The thermodynamic parameters are consistent with the mutation Tyr 49 3 Phe, producing a slight conformational change in the active site.

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Section: Figmentioning

confidence: 61%