O-2- GENERATION AND LIPID-PEROXIDATION DURING THE OXIDATION OF A GLYCATED POLYPEPTIDE, GLYCATED POLYLYSINE, IN THE PRESENCE OF IRON-ADP

Oxidation of glycated polylysine, a model compound of glycated protein, caused O2- production even at physiological pH, which could be accelerated by Fe3+-ADP. An enediol structure in glycated polylysine and related compounds, which could be confirmed by I2 uptake, was related to their oxidizability. Glycated polylysine was easily coordinated with Fe3+ even in the presence of phosphate at pH 7.4 and the formation of the iron complex was prevented by desferrioxamine. The exposure of unsaturated phospholipid liposomes to glycated polylysine-Fe3+-ADP system caused the production of a thiobarbituric acid-reacting substance, which was completely inhibited by 5 μM α-tocopherol or 150 /gmM desferrioxamine and slightly by 0.5 μM SOD. Catalase (20 μg/ml) and 10 mM sodium-benzoate did not affect the iron-glycated polylysine-induced lipid peroxidation, indicating no participation of an OH in this reaction. A ferrous ion-coordinated glycated polylysine may act as an initiator of phospholipid peroxidation in the presence of oxygen. A possible mechanism of the iron-glycated polylysine-induced lipid peroxidation was discussed. © 1990.