Conjugation of reduced glutathione to a wide number of exogenous and endogenous hydrophobic electrophiles (PubMed:22082028). Essential for ecdysteroid biosynthesis (PubMed:25344753, PubMed:25300303). May be involved in detoxification (PubMed:22082028). glutathione + RX = a halide anion + an S-substituted glutathione + H(+) Expressed in the adult ovary (at protein level). In early embryos expression is ubiquitous (PubMed:25344753). From mid-embryogenesis (stage 16) and throughout larval development, expressed in the prothoracic gland cells of the ring gland (PubMed:25344753, PubMed:25300303). Weak expression in the follicle cells of the ovarioles in developing egg chambers (at protein level) (PubMed:25300303). Embryonic lethal. Embryos display severe developmental defects such as poorly differentiated cuticle, failure of head involution, abnormal gut looping, and defective mouth hooks and dorsal closure (PubMed:25344753, PubMed:25300303). Trichromes are absent (PubMed:25344753). Embryos have a higher sterol content (PubMed:25344753, PubMed:25300303). Embryonic lethality, defective epidermal differentiation and trichome development can be rescued by supplementing embryos with 20-hydroxyecdysone (20E), ecdysone or cholesterol (PubMed:25344753). RNAi-mediated knockdown results in larval lethality at the second instar stage, which can be rescued by supplementing larvae with 20E, ecdysone or cholesterol (PubMed:25300303). Member of the Halloween gene group. Belongs to the GST superfamily. Epsilon family.