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The evolutionally conserved aspartyl residues (Asp57, Asp98 and Asp152) in human glutathione S-transferase P1-1 were replaced with alanine by site-directed mutagenesis to obtain the mutants (D57A, D98A and D152A). The replacement of Asp98 with alanine resulted in a decrease of the affinity for S-hexyl-GSH-agarose, a 5.5-fold increase of the KmGSH and a 2.9-fold increase of the I50 of S-hexyl-GSH for GSH-CDNB conjugation. Asp98 seems to participate in the binding of GSH through hydrogen bonding with the alpha-carboxylate of the gamma-glutamyl residue of GSH. The kcat of D98A was 2.6-fold smaller than that of the wild-type, and the pKa of the thiol group of GSH bound in D98A was approximately 0.8 pK units higher than those in the wild-type. Asp98 also seems to contribute to the activation of GSH to some extent. On the other hand, most of the kinetic parameters of D57A and D152A were similar to those of the wild-type. However, the thermostabilities of D57A and D152A were significantly lower than that of the wild-type. Asp57 and Asp152 seem to be important for maintaining the proper conformation of the enzyme.
K H Kong, and
H Inoue, and
K Takahashi
October 1992,
The Journal of biological chemistry,
K H Kong, and
H Inoue, and
K Takahashi
January 1995,
The Journal of biological chemistry,
K H Kong, and
H Inoue, and
K Takahashi
March 1991,
The Biochemical journal,
K H Kong, and
H Inoue, and
K Takahashi
November 1993,
The Journal of biological chemistry,
K H Kong, and
H Inoue, and
K Takahashi
October 2003,
Protein and peptide letters,
K H Kong, and
H Inoue, and
K Takahashi
July 1992,
The Biochemical journal,
K H Kong, and
H Inoue, and
K Takahashi
August 1992,
The Biochemical journal,
K H Kong, and
H Inoue, and
K Takahashi
August 2002,
IUBMB life,
K H Kong, and
H Inoue, and
K Takahashi
February 1994,
Cancer research,
K H Kong, and
H Inoue, and
K Takahashi
February 1998,
FEBS letters,
