Calcium stimulation of a novel 12-lipoxygenase from rat basophilic leukemia (RBL-1) cells.

Cytosolic fraction of RBL-1 cells transformed arachidonic acid to 12-HETE in addition to the well-recognized 5-hydroxyeicosatetraenoic acid (5-HETE) in the presence of Ca2+, Mg2+ or Mn2+. The identity of 12-HETE was confirmed by gas chromatography-mass spectrometry. Syntheses of 12-HETE and 5-HETE were catalyzed by separate lipoxygenases, since the formation of each product showed differential sensitivity to inhibitors and temperature. 12-Lipoxygenase from RBL-1 cells was also found to be distinct from the enzyme from platelets in calcium sensitivity.