Conjugation of reduced glutathione to a wide number of exogenous and endogenous hydrophobic electrophiles. glutathione + RX = a halide anion + an S-substituted glutathione + H(+) Homodimer. In liver, highest expression found in central vein limiting plate hepatocytes. Also expressed in interlobular bile duct epithelial cells. In lung, expressed in Clara cells and ciliated cells of the bronchiolar epithelium and in type II alveolar cells of the lung parenchyma. Belongs to the GST superfamily. Theta family.