Glutathione transferase A1-1: catalytic role of water

For more than almost 30 years now, glutathione transferases (GSTs) have been known as xenobiotic/endobiotic detoxification enzymes. GSTs catalyze the nucleophilic addition of glutathione (GSH) sulphur thiolate to a wide range of electrophilic substrates, building up a less toxic and more soluble compound, which can then be removed from the cell. Recently we proposed a consistent GSH activation mechanism. By performing QM/MM calculations, we demonstrated that a water molecule, following a first conformational rearrangement of GSH, is capable of assisting a proton transfer between the GSH thiol and alpha carboxylic groups. In this study we go further in the analysis of the water role in GSH activation by performing a long Molecular Dynamics (MD) study on glutathione transferase A1-1 Thr68 mutants complexed with GSH and the GSH decarboxylated analogue (dGSH), for which experimental kinetic data are available.