Propylthiouracil inducible glutathione transferases. Selective induction of ligandin (glutathione transferase 1-1).

Repeated administration of propylthiouracil (PTU) resulted in an increase in glutathione (GSH) transferases activity in rat liver cytosol toward various substrates except for epoxy(p-nitrophenoxy)propane. The enzyme from rat treated with PTU showed high activity with 1-chloro-2,4-dinitrobenzene (CDNB) and ethacrynic acid. GSH transferases were separated into five forms by CM-Sephadex C-50 column chromatography to detect which isozymes were induced by PTU treatment. Although the activity of the unretained fraction obtained from the column was slightly increased by PTU treatment, the treatment markedly elevated the activity of GSH transferase 1-1. On the other hand, the activities of GSH transferases 1-2, 3-3 and 2-2 were little changed. In addition, an analysis of GSH transferase 1-1 from CM-Sephadex C-50 using SDS-PAGE confirmed that it comprised the 1-1 homodimer. This fraction was then further purified by passing it through a hydroxylapatite column and the partially purified GSH transferase 1-1 from rats treated with PTU was found to have the same characteristics as the control, e.g. the same Km values for GSH and CDNB and the same substrate spectrum. It was concluded that PTU specifically induced GSH transferase 1-1 among the cationic transferases.