Interaction of low-density lipoproteins of serum with hemin

Abstract

The interaction of low-density lipoproteins of human serum with hemin and the nature of the oxidative denaturation of low-density lipoproteins of serum catalyzed by hemin was studied by means of spectrophotometric and ultracentrifugal analyses and by manometric methods. The results indicated that a complex was formed in vitro between hemin and isolated serum low-density lipoproteins. The peroxidation of the low-density lipoproteins was enhanced in the presence of low concentrations of hemin, approximately 1 to 10 mg of hemin per gram of lipoproteins. At higher concentrations, the catalytic effect of the hemin was depressed. Progressive increases in the amount of hemin associated with the lipoproteins and progressive decreases in the flotation rate of the lipoproteins were noted as more hemin was added. In unfractionated serum, a preferential association of hemin with the albumin fraction and with high-density lipoproteins minimized the association of hemin with low-density lipoproteins. Although the mode of association between isolated low-density lipoproteins and hemin was not clarified, most of the hemin molecules appeared to associate loosely with the protein moieties of low-density lipoproteins.