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Enhanced Lipid Oxidation by Oxidatively Modified Myoglobin: Role of Protein-Bound Heme

https://doi.org/10.1006/bbrc.2000.2349Get rights and content

Abstract

The formation of oxidized low density lipoprotein (LDL) is believed to play a significant role in the pathogenesis of atherosclerosis. Myoglobin in the presence of H2O2 has been shown to catalyze LDL oxidation in vitro. It is established that an oxidatively altered form of myoglobin (Mb-H), which contains a prosthetic heme covalently crosslinked to the apoprotein, is a major product in the reaction of native myoglobin with peroxides. In the current study, we have shown for the first time that Mb-H, in the absence of exogenously added peroxides, oxidizes LDL and purified lipids, as determined by the formation of conjugated dienes, lipid peroxides, and thiobarbituric acid reactive substances. Moreover, the rate of oxidation of pure phosphatidylcholine by Mb-H was found to be at least sevenfold greater than that observed for native myoglobin. The current study strongly suggests a role for Mb-H in the lipid peroxidation observed with myoglobin.

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Abbreviations used: LDL, low density lipoprotein; Ox-LDL, oxidized low density lipoprotein; Mb-H, protein-bound heme adducts of myoglobin; TBARS, thiobarbituric acid reactive substances; EDTA, (Ethylene-dinitrilo)-tetraacetic acid; PAPC, palmitoyl arachidonoyl phosphatidylcholine; CA, cholesteryl arachidonate

1

To whom correspondence should be addressed at Department of Pharmacology, The University of Michigan Medical School, 1301 Medical Science Research Building III, Ann Arbor, MI 48109-0632. Fax: (734) 763-4450. E-mail: [email protected].

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