Identification of modified tryptophan residues in apolipoprotein B-100 derived from copper ion-oxidized low-density lipoprotein.
نویسندگان
چکیده
Oxidative modifications of low-density lipoproteins (LDL) may contribute to the pathogenesis of atherosclerosis. Although the oxidation products of the lipid components of LDL have been studied extensively, less is known about the oxidation products of the apoprotein, apolipoprotein B-100. To identify the specific oxidative modifications, we oxidized LDL in the presence of Cu(2+), treated with DNPH, precipitated and delipidated the protein, digested the protein with trypsin, and analyzed the peptides by high-performance liquid chromatography. We isolated nine peptides that exhibited measurable absorbance at 365 nm, which is characteristic of hydrazones derived from DNPH and is not observed in peptides derived from unoxidized LDL. Unexpectedly, we obtained the same peptides with absorbance at 365 nm in Cu(2+)-oxidized LDL not treated with DNPH. N-terminal sequence analyses and mass spectrometry indicated that the peptides isolated from the Cu(2+)-oxidized LDL all contained kynurenine residues in place of Trp residues found in the native apoprotein. The product profile we observed in Cu(2+)-oxidized LDL was remarkably different from the profiles observed in LDL oxidized by HOCl or myeloperoxidase in vitro, and the preferential oxidation of Trp to kynurenine in Cu(2+)-catalyzed oxidation of LDL contrasts with the products observed following oxidation of LDL with HOCl or myeloperoxidase. Our studies to date support the working hypothesis that the specific products of protein oxidation are sufficiently distinct to be developed as biomarkers of proposed mechanisms of oxidation of LDL and biological molecules in other toxicities and diseases.
منابع مشابه
Mapping oxidations of apolipoprotein B-100 in human low-density lipoprotein by liquid chromatography-tandem mass spectrometry.
Human low-density lipoprotein (LDL) is a major cholesterol carrier in blood. Elevated concentration of low-density lipoprotein, especially when oxidized, is a risk factor for atherosclerosis and other cardiac inflammatory diseases. Past research has connected free radical initiated oxidations of LDL with the formation of atherosclerotic lesions and plaque in the arterial wall. The role of LDL p...
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عنوان ژورنال:
- Biochemistry
دوره 38 48 شماره
صفحات -
تاریخ انتشار 1999