Inhibition of platelet lipoxygenase by toluene-3,4-dithiol and other ferric iron chelators

Arachidonate lipoxygenase, obtained from the soluble, cytoplasmic fraction of sonicated human platelets was strongly inhibited by toluene-3,4-dithiol and dithizone, agents which form strong complexes with ferric but not ferrous ions. Weak inhibition was noted with the less specific iron chelator ortho-phenanthroline and with potassium cyanide. There was no inhibition with the ferrous iron chelating agent 2,2′ dipyridyl nor with bathophenanthroline or EDTA. These findings suggest that platelet lipoxygenase activity depends on ferric iron.