Acts a maleylacetone isomerase. Also catalyzes the glutathione-dependent dehalogenation of dichloroacetic acid to glyoxylic acid. In vitro, possesses glutathione peroxidase activity toward cumene hydroperoxide and linoleic acid-13-hydroperoxide. glutathione + RX = a halide anion + an S-substituted glutathione + H(+) Homodimer. By salicylic acid, methyl jasmonate, auxin, H(2)O(2), and the pathogen Hyaloperonospora parasitica. Belongs to the GST superfamily. Zeta family.