DIFFERENCES IN THE ANTIOXIDANT MECHANISM OF CARNOSINE IN THE PRESENCE OF COPPER AND IRON

Carnosine is a beta-alanylhistidine dipeptide found in skeletal muscle. Carnosine (1.0-25 mM) is capable of inhibiting copper- and iron-catalyzed oxidation of phosphatidylcholine liposomes as measured by thiobarbituric acid reactive substances (TBARS) and lipid peroxides. The ability of 5 mM carnosine to inhibit the formation of TBARS and lipid peroxides was 2.5- and 8.8-fold higher, respectively, for copper- than iron-catalyzed lipid oxidation. Carnosine (0.05-10.0 mM) is capable of inhibiting copper-catalyzed oxidation of ascorbic acid but was ineffective at preventing iron-catalyzed ascorbate oxidation. Carnosine inhibits iron-dependent microsomal lipid oxidation but does not inhibit the oxidation of NADPH by the enzyme system. H-1 NMR spectra of carnosine show peak broadening in the presence of copper but not iron. These data suggest that carnosine forms a complex with copper which decreases its catalytic activity; however, carnosine does not form a complex with iron.