Active as '1-Cys' thiol transferase against beta-hydroxyethyl disulfide (HED), as dehydroascorbate reductase and as dimethylarsinic acid reductase, while not active against the standard GST substrate 1-chloro-2,4-dinitrobenzene (CDNB). glutathione + RX = a halide anion + an S-substituted glutathione + H(+) Up-regulated by tert-butyl hydroperoxide (t-BOOH) in an MSN2/4-dependent manner. Belongs to the GST superfamily. Omega family.