Oxygen-mediated heterogeneity of apo-low-density lipoprotein.

Abstract

Mild oxidation of human serum low-density lipoprotein (LDL) converts the apoprotein from a nearly homogeneous component of high apparent MW to a mixture of apparently lower MW polypeptide components, as characterized by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. This protein alteration, which correlates temporally with increases in the formation of lipid oxidation products and in the fluorescence of the apoprotein , is markedly reduced when oxygen is excluded or when EDTA or the free-radical-scavenging antioxidants, butylated hydroxytoluene or propyl gallate, are added. The conversion thus appears to be due to a reaction between the protein moiety and auto-oxidizing lipid. The presence of the antibacterial agent sodium azide markedly accelerates the oxidation, suggesting that it should only be used with caution in lipid-containing solutions.