Catalyzes the conjugation of leukotriene A4 with reduced glutathione (GSH) to form leukotriene C4 with high specificity (PubMed:23409838, PubMed:27365393, PubMed:27791009, PubMed:7937884, PubMed:9153254). Can also catalyze the transfer of a glutathionyl group from glutathione (GSH) to 13(S),14(S)-epoxy-docosahexaenoic acid to form maresin conjugate in tissue regeneration 1 (MCTR1), a bioactive lipid mediator that possess potent anti-inflammatory and proresolving actions (PubMed:27791009).