Calcium regulation of the human PMN cytosolic 15-lipoxygenase.
Addition of tracer (pg) amounts of [3H]arachidonic acid to the 120,000 x g cytosolic fraction of human polymorphonuclear leukocytes (PMNs) produced [3H]-15-HETE, the product of the 15-lipoxygenase, as the major metabolite. In the presence of nanomolar and low micromolar amounts of calcium, [3H]-15-HETE formation was increased as much as 15-fold which corresponded to 17% conversion of added substrate. This enhancement of the cytosolic 15-lipoxygenase activity, which was reversible by EGTA, was inhibited by phosphatidyl serine and phosphatidyl choline. Millimolar levels of calcium inhibited the cytosolic 15-lipoxygenase and the 5-lipoxygenase product 5-HETE could reverse this inhibition. These results indicate that calcium is an important modulator of the PMN 15-lipoxygenase when the enzyme is in a cytosolic milieu.
Nichols
R C
RC
Department of Biochemistry and Molecular Biology, George Washington University-School of Medicine and Health Sciences, Washington, DC 20037.
Vanderhoek
J Y
JY
D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism*; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D002118:Calcium / Q000502:physiology*; D003600:Cytosol / Q000201:enzymology; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis; D016859:Lipoxygenase Inhibitors; D009504:Neutrophils / Q000201:enzymology*; D010713:Phosphatidylcholines / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism
D006893:Hydroxyeicosatetraenoic Acids; D016859:Lipoxygenase Inhibitors; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; D001093:Arachidonate 15-Lipoxygenase; D001094:Arachidonate 5-Lipoxygenase; D002118:Calcium