Functional analysis of the evolutionary conserved arginine 182 residue in human glutathione S-transferase P1-1

Abstract

The mutational replacement of Arg182 with threonine markedly decreased the specific activities for GSH-conjugation reaction. The k(cat) of R182T for GSH-[1-chloro-2,4-dinitrobenzene] conjugation reaction was about 100-fold smaller than that of the wild type. On the other hand, the affinity for GSH of R182T was not significantly affected. The pK(a) of the thiol group of GSH bound in R182T was similar to 0.9 pK units higher than those in the wild type, but the k(cat)/K-m(1-chloro-2,4-dinitrobenzene) values at high pH were not so much lower than those of the wild type. The thermostability of R182T was significantly lower than that of the wild type. Therefore, Arg182 seems to be important for the construction of the active enzyme structure.