THE EFFECT OF METAL-CATIONS ON COPPER-CAT ALYZED PEROXIDATION OF LOW-DENSITY LIPOPROTEINS

The effect of metal cations on copper-catalyzed lipid peroxidation (LP O) of low density lipoproteins (LDL) was examined. The presence of met al cations in the incubation media containing LDL (0,8 mg protein/ml) and CuSO4 (0-80 mu M) influenced on LPO of LDL as evident by the measu rement of TBARS. With the concentrations of CuSO4 less than 10 mu M, t he metal cations caused an increase in LDL peroxidation. Zn2+ appeared to be the most effective inductor, Mn2+ was less effective, and the i nfluence of Ca2+ and Mg2+ was insignificant. With greater CuSO4 concen trations Mg2+ showed no effect on TEARS formation in LDL while the add ition of other nontransition metal cations to the incubation mixture l ed to the inhibition of LDL peroxidation. The capacity for inhibition decreased in the row Mn2+ > Zn2+ > Ca2+ > Mg2+. The possible mechanism explaining these results may be in the competition of metal ions for copper binding sites on LDL. Our results allow to suggest the existenc e of two types of copper binding sites on LDL, tight-binding sites whi ch are non-effective In LPO and effective weak-binding sites.