The role of phospholipids in regulation of activity of porcine leukocyte 12-lipoxygenase

12-Lipoxygenase from porcine leukocytes was partially purified by using of DEAE-Toyopearl chromatography (pH 7,5). Phosphatidylcholine and Phosphatidylinositol in reaction mixtures with mixed micelles Lubrol PX / linoleic acid inhibited the enzyme. The pH-optimum of lipoxygenase reaction in presence of phospholipids shifted into alkaline region. In the absence of phospholipids 3 additional substrate molecules bound with enzyme-substrate complex. In the presence of either phosphatidylcholine of phosphatidylinositol up to 2 substrate molecules bound with enzyme-substrate complex. The phospholipids competed with linoleic acid for one of the enzyme binding centers. A kinetic scheme of 12-lipoxygenase reaction has been proposed: formula represented Phosphatidylinositol lowered the values of K_s and K_ns of the reaction of linoleic acid oxydation by 12-lipoxygenase, while phosphatidylcholine had opposite effect on these parameters. We suppose that phospholipids can regulate 12-lipoxygenase activity via control of the enzyme affinity to the substrate (polyunsaturated fatty acid).