Glutathione transferase from rat testis

Glutathione transferases play an important role in the biotransformation and detoxication of electrophilic xenobiotics. The occurrence of glutathione transferase in animal species is widespread. Several transferase isoenzymes are isolated from rat liver. Six basic transferase isoenzymes in rat hepatic cytosol are characterized as binary combinations of four protein subunits. The presence of glutathione transferase is not restricted to the liver but also is demonstrated in extrahepatic organs. However, in comparison with the liver most other organs show considerably lower activity. One exception is rat testis, which also shows high transferase activity. In contrast with liver, and most other organs, a major part of the glutathione transferase activity in rat testis is borne by an isoenzyme, glutathione transferase 6-6, with an acidic isoelectric point. The purification of this enzyme, which accounts for approximately 50% of the cytosolic glutathione transferase activity, is described in this chapter. In addition to this major acidic isoenzyme, smaller amounts of the basic species, glutathione transferases 2-2, 3-3, 3-4, and 4-4 are identified in testis.