GSTM1 is a glutathione S-transferase that belongs to the mu class. This enzyme acts by catalyzing the reaction of glutathione with an acceptor molecule to form an S-substituted glutathione (S=sulfur). The reactions utilizing glutathione contribute the transformation of a wide variety of electrophiles, including reactive products of lipid, protein, carcinogens, therapeutic drugs, environmental toxins, and products of oxidative stress. Recombinant GSTM1 protein was expressed in E.coli and purified by using conventional chromatography techniques.