Glutathione S-transferase subunits in the mouse and their catalytic activities towards reactive electrophiles.

The glutathione S-transferases (GST) are a major, multi-gene, group of detoxication proteins. A rapid, two-step purification, that employs S-hexylglutathione affinity chromatography and hydroxyapatite HPLC, is described for the GST isoenzymes in mouse liver. The major hepatic forms comprise Yf(Mr 24,500)-, Ya(Mr 26,000)- and Yb(Mr 27,000)-type subunits. The isoelectric points of the Yf, Ya and Yb dimers are 8.6, 9.2 and 7.8-8.2 respectively. Immunochemical experiments showed the purified mouse subunits cross-reacted with antisera raised against rat GST subunits that possessed equivalent molecular masses; the subunit sizes of the distinct subunit types are conserved between these two species. The catalytic activities of the purified mouse GST subunits are described. In common with other species the mouse GST are subject to tissue-specific expression. However, only mouse liver and not rat, guinea pig, hamster or human livers express the Yf polypeptide. The significance of this difference is unclear but, in the rat, the Yf subunit can serve as a marker for pre-neoplastic hepatocellular carcinogenesis.