CALCIUM PROMOTES MEMBRANE ASSOCIATION OF RETICULOCYTE 15-LIPOXYGENASE

The reticulocyte 15-lipoxygenase (linoleate:oxygen oxido-reductase, EC 1.13.11.12) is implicated in oxidative damage to reticulocyte mitocho ndria before their elimination by degradation during maturation to the erythrocyte. A proportion of the 15-lipoxygenase sediments with the m itochondrial-rich stromal fraction of density-gradient-fractionated ra bbit reticulocytes suggesting a physical association with mitochondria before their elimination. Ca2+ promotes binding of reticulocyte 15-li poxygenase to isolated rat liver and reticulocyte mitochondria and 15- lipoxygenase-mediated lipid peroxidation of mitochondrial lipids and f ree linoleic acid. Association of reticulocyte 15-lipoxygenase with is olated mitochondria is not simply a consequence of Ca2+-induced swelli ng, but implies that Ca2+ mediates translocation of soluble lipoxygena se to mitochondrial membranes. Therefore, Ca2+ may have an important p hysiological role in the regulation of 15-lipoxygenase-mediated target ing of reticulocyte mitochondria for degradation.