Glutathione S-transferase that catalyzes the nucleophilic attack of the sulfur atom of glutathione on the electrophilic groups of a wide range of exogenous and endogenous compounds (Probable). Involved in the formation of glutathione conjugates of both prostaglandin A2 (PGA2) and prostaglandin J2 (PGJ2). It also catalyzes the isomerization of D5-androstene-3,17-dione (AD) into D4-androstene-3,17-dione and may therefore play an important role in hormone biosynthesis. Through its glutathione-dependent peroxidase activity toward the fatty acid hydroperoxide (13S)-hydroperoxy-(9Z,11E)-octadecadienoate/13-HPODE it is also involved in the metabolism of oxidized linoleic acid (By similarity). glutathione + RX = a halide anion + an S-substituted glutathione + H(+) glutathione + prostaglandin A2 = prostaglandin A2-S-(R)-glutathione glutathione + prostaglandin J2 = prostaglandin J2-S-(R)-glutathione (13S)-hydroperoxy-(9Z,11E)-octadecadienoate + 2 glutathione = (13S)-hydroxy-(9Z,11E)-octadecadienoate + glutathione disulfide + H2O androst-5-ene-3,17-dione = androst-4-ene-3,17-dione Homodimer (PubMed:11119643). Homodimer or heterodimer of GSTA1 and GSTA2 (By similarity). In addition to its enzymatic activity, the homodimer of Ya chains, called ligandin, binds various organic anions, xenobiotics, and azocarcinogen dyes. Belongs to the GST superfamily. Alpha family.