Leukotriene A4: Enzymatic conversion to leukotriene C4

An unstable epoxide, leukotriene A4 (5(S)- trans -5,6-oxido-7,9- trans -11,14- cis -eicosatetraenoic acid), was earlier proposed to be an intermediate in the conversion of arachidonic acid into the slow reacting substance (SRS), leukotriene C4. In the present work synthetic leukotriene A4 was incubated with human leukocytes or murine mastocytoma cells. A lipoxygenase inhibitor, BW755C, was added in order to prevent leukotriene formation from endogenous substrate. Leukotriene C4 and 11- trans -leukotriene C4 were the main products with SRS activity. It was not established whether the 11- trans -compound was formed by isomerization at the leukotriene A4 or C4 stage.