4.4.1.20 leukotriene C4 = leukotriene A4 + glutathione - - 4.4.1.20 leukotriene C4 = leukotriene A4 + glutathione random rapid equilibrium mechanism 644489 4.4.1.20 leukotriene C4 = leukotriene A4 + glutathione the thiolate of glutathione acts as a nucleophile attacking C6 of leukotriene A4 forming a S-C6 bond, a proton is transferred from the guanidinium of Arg31 to the epoxide ring oxygen resulting in opening of the epoxide ring and stabilization of the LTC4 product complex. The tail-to-head orientation appears to be the most likely substrate orientation 730555