Interaction of human 15-lipoxygenase-1 with phosphatidylinositol bisphosphates results in increased enzyme activity

Abstract

15-lipoxygenase-1 (15-LO-1) can oxygenate both free fatty acids and fatty acids bound to membrane phospholipids. The regulation of the activity of membrane associated 15-LO-1 is poorly understood. Here we demonstrate that calcium ionophore stimulates the translocation of 15-LO-1 to the plasma membrane in human dendritic cells. In a protein–lipid overlay assay, 15-LO-1 was capable of interacting with several phosphoinositides. In the presence of calcium, addition of phosphatidylinositol-4.5-bisphosphate (PI(4.5)P 2) or PI(3.4)P 2 to the vesicles containing arachidonic acid, led to the formation of approximately three times more 15-HETE than vesicles without phosphoinositides and up to seven times more 15-HETE than vesicles without both calcium and phosphoinositides. The Vmax was unchanged but the apparent Km of 15-LO-1 towards arachidonic acid was significantly lower in the presence of PI(4.5)P 2 or PI(3.4)P 2 in the vesicles in comparison to vesicles with PC only. Taken together, this report demonstrates that human 15-LO-1 binds to PI(4.5)P 2 and PI(3.4)P 2 and that these phospholipids stimulate enzyme activity in the presence of calcium in a vesicle based assay.