Studies on arachidonate 5-lipoxygenase of rat basophilic leukemia cells

Arachidonate 5-lipoxygenase was partially purified from rat basophilic leukemia cells with the aid of ATP as a ligand linked to Sepharose. The enzyme produced predominantly 5-hydroperoxy-6,8,11,14-eicosatetraenoic acid. Calcium ion was required for the enzyme activity (0.1 mM for half maximal activity), and the calcium-dependent reaction was stimulated by ATP and several nucleotides. 5,8,11,14,17-Eicosapentaenoic acid was converted to its 5-hydroperoxy derivative at a higher rate than arachidonate oxygenation. 5,8,11-Eicosatrienoic acid as substrate was almost as active as arachidonic acid. Among various lipoxygenase inhibitors tested, cirsiliol, a flavone derivative, was the most potent.