Conjugation of reduced glutathione to a wide number of exogenous and endogenous hydrophobic electrophiles. May also function as a storage protein or ligandin for parasitotoxic ferriprotoporphyrin IX (hemin). glutathione + RX = a halide anion + an S-substituted glutathione + H(+) Inhibited by chloroquine, cibacron blue, ferriprotoporphyrin IX (hemin) and S-hexylglutathione. Optimum pH is 8.1. Homodimer. In the absence of ligands two homodimers may interact to form a tetramer. Belongs to the GST superfamily.