GSTM4 (glutathione S-transferase mu 4) is a Phase II detoxification enzyme that catalyzes the conjugation of reduced glutathione (GSH) to various exogenous and endogenous hydrophobic electrophiles 1. The enzyme exhibits dual functionality in xenobiotic metabolism and specialized lipid mediator biosynthesis. GSTM4 can catalyze leukotriene A4 conjugation with GSH to form leukotriene C4, and also transfers glutathionyl groups to 13S,14S-epoxy-docosahexaenoic acid to produce maresin conjugate in tissue regeneration 1 (MCTR1), a bioactive anti-inflammatory and pro-resolving lipid mediator 2. The protein functions as a homodimer with glutathione transferase activity and is highly expressed in liver hepatocytes 3. GSTM4 shows broad tissue expression including heart, placenta, lung, brain, liver, skeletal muscle, and various cell lines 1. Recent studies suggest clinical relevance, with genetic variants associated with migraine risk through Mendelian randomization analyses 4 and potential therapeutic targeting in oral cancer 5. The gene contains eight exons and is subject to alternative splicing variants that may affect protein function 6.