Leukotriene A4 conjugates with reduced glutathione (GSH) to produce leukotriene C4 (LTC4). This conjugation is mediated by the homodimeric, perinuclear membrane-bound enzyme leukotriene C4 synthase (LTC4S) (Lam et al. 1994, Welsch et al. 1994). LTC4S differs from cytosolic and microsomal GSH-S-transferases by having a very narrow substrate specificity and the inability to conjugate xenobiotics.