Myeloperoxidase binds to low‐density lipoprotein: potential implications for atherosclerosis

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Abstract
Myeloperoxidase (MPO), an abundant heme enzyme released by activated phagocytes, catalyzes the formation of a number of reactive species that can modify low‐density lipoprotein (LDL) to a form that converts macrophages into lipid‐laden or ‘foam’ cells, the hallmark of atherosclerotic lesions. Since MPO has been shown to bind to a number of different cell types, we investigated binding of MPO to LDL. Using the precipitation reagents phosphotungstate or isopropanol, MPO co‐precipitated with LDL, retaining its catalytic activity. The association of MPO with LDL was confirmed using native gel electrophoresis. MPO was also found to co‐precipitate with apolipoprotein B‐100‐containing lipoproteins in whole plasma. No precipitation of MPO was observed in lipoprotein‐deficient plasma, and there was a dose‐dependent increase in precipitation following addition of LDL to lipoprotein‐deficient plasma. Binding of MPO to LDL could potentially enhance site‐directed oxidation of the lipoprotein and limit scavenging of reactive oxygen species by antioxidants.