Conjugation of reduced glutathione to a wide number of exogenous and endogenous hydrophobic electrophiles. Involved in the formation of glutathione conjugates of both prostaglandin A2 (PGA2) and prostaglandin J2 (PGJ2). Participates in the formation of novel hepoxilin regioisomers. Regulates negatively CDK5 activity via p25/p35 translocation to prevent neurodegeneration. glutathione + RX = a halide anion + an S-substituted glutathione + H(+) glutathione + prostaglandin J2 = prostaglandin J2-S-(R)-glutathione glutathione + prostaglandin J2 = prostaglandin J2-S-(S)-glutathione glutathione + prostaglandin A2 = prostaglandin A2-S-(S)-glutathione 11(S)-hydroxy-14(S),15(S)-epoxy-(5Z,8Z,12E)-eicosatrienoate + glutathione = (11S,15S)-dihydroxy-14(R)-S-glutathionyl-(5Z,8Z,12E)-eicosatrienoate Homodimer. Interacts with CDK5. The 83 N-terminal amino acids function as un uncleaved transit peptide, and arginine residues within it are crucial for mitochondrial localization. Belongs to the GST superfamily. Pi family.