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 l ipid oxidation in the presence of reducing compounds. Ascorbate (100 m uM) 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 oxi dation was inhibited by EDTA, ceruloplasmin, catalase and superoxide d ismutase indicating the involvement of iron, hydrogen peroxide and sup eroxide anion. Both lipid oxidation and the release of iron from the i nsoluble fraction increased with increasing pH (5.0-7.0) in the presen ce of ascorbate. Iron bound to the insoluble components of beef muscle could be involved in catalysis of lipid oxidation.