Importance of the Hydroxyl Group of Ser65 for Glutathione Binding of Human Glutathione S-transferase P1-1

Abstract

The mutational replacement of Ser65 with alanine decreased the binding affinity of the enzyme for S-hexyl-GSH-Sepharose and GSH-agarose, and increased the K_mGSH value and I_(50) inhibitory effect for S-hexyl-GSH, but did not significantly affect the k_(cat) value for glutathione conjugation with 1-chloro-2,4-dinitrobenzene. The pKa value of the thiol group of GSH bound in S65A was shifted approximately 0.6 pK units higher than the pKa value in the wild type. Therefore, Ser65 seems to contribute to the binding of GSH.