Role of glutathione S-transferases in detoxification of a polycyclic aromatic hydrocarbon, methylcholanthrene

Glutathione S-transferases (GSTs), the versatile phase II biotransformation enzymes, metabolize and detoxify a wide variety of toxic chemical compounds like carcinogens, chemotherapeutic drugs, environmental pollutants and oxidative stress products. GSTs are currently of great interest in drug discovery, nanotechnology and biotechnology because of their involvement in many major cellular processes. GSTs, which are either homo or hetero dimeric proteins mediate catalytic binding between glutathione (GSH) and an array of either endogenous or exogenous toxic compounds to form a highly soluble detoxified complex which is then eliminated. Polycyclic aromatic hydrocarbons (PAHs) which are composed of two or more benzene rings bonded as linear, cluster or angular arrangements are used as intermediaries in pharmaceuticals, agricultural products, photographic products, thermosetting plastics, lubricating materials and other chemical products. Foods those cooked at high temperatures by grilling, roasting, frying and smoking are the main sources for the persistent bio-accumulation of PAHs in food chain. The carcinogenic, mutagenic and immunosuppressive effects of PAHs are well established. A well-known polycyclic aromatic hydrocarbon, methylcholanthrene is a potential carcinogenic, neurotoxic, mutagenic and tumour causing agent that is used as an experimental carcinogen in biological research. Methylcholanthrene converts into reactive metabolites when it enters living cells and those reactive metabolites oxidize DNA, RNA, proteins and lipids and form DNA and protein adducts as well. GSTs play major role in the detoxification of reactive metabolites of methylcholanthrene by mediating catalytic binding with GSH to form a highly soluble detoxified complex which is then eliminated. This review summarizes the role of GSTs in the detoxification of a polycyclic aromatic hydrocarbon, methylcholanthrene.