Glutathione S-transferases (GSTs) function in the metabolic detoxification of various environmental carcinogens and lipid hydroperoxides. Members of the murine GSTP (glutathione S-transferase pi) family, termed Gstp1 and Gstp2, are linked to drug resistance and are markers for many cancers. Gstp proteins modulate cell signaling by interacting with c-Jun N-terminal kinase (JNK), and may play a protective role in the development of spontaneous tumors. Gstp has been found in substantia nigra and may be associated with reactive oxygen species-induced neurological disorders such as Parkinson’s disease and may additionally protect against endothelial dysfunction induced by tobacco smoke exposure.