Catalysis of lipid oxidation by iron from an insoluble fraction of beef diaphragm muscle

An insoluble fraction of beef diaphragm muscle was found to catalyze lipid oxidation in the presence of reducing compounds. Ascorbate (100 micromolar) catalyzed the formation of thiobarbituric acid reactive substances 3.3, 8.3 and 7.3-fold more effectively than cysteine, superoxide and NADPH, respectively. Ascorbate/insoluble fraction-catalyzed lipid oxidation was inhibited by EDTA, ceruloplasmin, catalase and superoxide dismutase indicating the involvement of iron, hydrogen peroxide and superoxide anion. Both lipid oxidation and the release of iron from the insoluble fraction increased with increasing pH (5.0-7.0) in the presence of ascorbate. Iron bound to the insoluble components of beef muscle could be involved in catalysis of lipid oxidation