Measurement of 5-hydroxy-2-aminovaleric acid as a specific marker of iron-mediated oxidation of proline and arginine side-chain residues of low-density lipoprotein apolipoprotein B-100.

An alteration of apolipoprotein (apo) B-100 structure by direct oxidative modification is supposed to be an important mechanism involved in atherogenesis. There is difficulty in quantifying this type of modification owing to a lack of specific assays. We evaluated a methodology based on the oxidation of protein arginine and proline to gamma-glutamyl semialdehyde which by reduction forms 5-hydroxy-2-aminovaleric acid (HAVA). We determined HAVA by using derivatization to N(O)-ethoxycarbonyl ethyl esters and gas chromatography-mass spectrometry in different low-density lipoprotein preparations subjected to oxidative damage in the presence of iron. Results suggest that apoB-100 proline and arginine residues are highly reactive toward oxygen radicals ex vivo. Femtomole levels of HAVA can be reproducible measured. HAVA determination compares well with the measurement of carbonyl group formation used as a generally accepted but nonspecific index of protein oxidation. Thus, HAVA could prove to be a sensitive assay for studying specific modification of apoB-100. Copyright 2000 Academic Press.