Differential activities of rat and human lung glutathione S-transferase isoenzymes towards benzo(a)pyrene epoxides.

The isoenzymes of human and rat lung glutathione S-transferase (GST) differ among themselves in their activities towards the epoxides of benzo(a)pyrene (BP). The Ya' and Yc-type subunits of rat lung GST exhibit maximum activities towards BP-4,5-oxide and BP-7,8-oxide suggesting that these two subunits are preferentially involved in the detoxification of highly reactive epoxides and diol-epoxides of polycyclic aromatic hydrocarbons (PAH). The studies with human lung GST isoenzymes indicate that BP-4,5-oxide, and BP-7,8-oxide are preferred substrates for the cationic (pI 8.3) form of the enzyme. Identification of compounds which can selectively induce these isoenzymes of GST could prove useful as inhibitors of PAH induced neoplasia.