Maintains high levels of reduced glutathione in the cytosol (PubMed:23593298). Involved in resistance to oxidative stress and starvation (PubMed:23593298). Together with thioredoxin reductase txtr-1, required for the reduction of disulfide groups in the cuticle during molting (PubMed:21199936). 2 glutathione + NADP(+) = glutathione disulfide + H(+) + NADPH Binds 1 FAD per subunit. Expressed at all larval stages and in adults in intestine, vulva muscle, pharynx and some cells in the tail. Induced by the oxidant juglone and starvation. RNAi-mediated knockdown causes a severe decrease in survival upon treatment with oxidants including juglone, paraquat and to a lesser extent, cumen and tert-butylhydroperoxide (tBOOH). Enhances further the production of gamma-glutamylycysteine and glutathione disulfide upon juglone treatment. Increases gst-4 and gcs-1 expression. Reduces lifespan (PubMed:23593298). RNAi-mediated knockdown in a trxr-1 mutant background causes an arrest during larval molting characterized by a partial detachment of the old cuticle and an impaired ability to reduce cuticle components (PubMed:21199936). Belongs to the class-I pyridine nucleotide-disulfide oxidoreductase family.