Peroxidase-dependent metal-independent oxidation of low density lipoprotein in vitro: a model for in vivo oxidation?

Oxidative modification of low density lipoprotein is believed to be an important pathway by which the lipoprotein becomes atherogenic. The in vitro systems for oxidative modification of low density lipoprotein thus far described all appear to depend upon the presence in the medium of free transition metal ions (copper or iron). In vivo, on the other hand, these metals are present almost exclusively in tightly complexed forms that do not catalyze oxidative modification. The present studies describe oxidation of low density lipoprotein in a simple system that does not depend upon the presence of added free metal ions. It requires the presence of horseradish peroxidase and either hydrogen peroxide or lipid hydroperoxides.