Human pi class glutathione S-transferase: anticancer material and functional study

Abstract

Glutathione S-transferase are a family of Phase II detoxification enzymes that catalyse the conjugation of glutathione to a wide variety of xenobiotics. To gain further insight into the relationship between structure and function of glutathione S-transferase, the four cystein mutants and the three Tyr108 mutants of hGSTP1-1 were expressed in E. coli and purified to electrophoretic homogeneity by affinity chromatography on immobilized GSH. The mutants were characterized that kinetic analysis and inhibition effects. The all cystein residues are not needed for the steroid isomerase activity of hGSTP1-1. The effect of substitutions on kinetic parameters suggests that Tyr108 in hGSTP1-1 contribute to the binding of the electrophilic substrate and a major determinant in the binding of CDNB in the aromatic ring of Tyr108, not its hydroxyl group. In order to search for bioactive natural products exerting inhibitory activity toward glutathione S-transferase, twenty natural products extracts were screened for inhibition or activation of hGSTP1-1. As results, we found significant inhibition of GST by methanolic extracts of Vucia unijuga, Sedum sarmentosum and Pelasiles japonicus BUNGE.