Mass spectrometric identification of modifications to human serum albumin treated with hydrogen peroxide.

Oxidized amino acid residues in human serum albumin exposed to hydrogen peroxide have been identified in tryptic peptides using liquid secondary ion mass spectrometry. Sites of oxidation identified include Cys34, Met123, Met298, Met446, and Met548. The extent of oxidation varied with location in the protein sequence, suggesting a relationship between oxidation and protein three-dimensional structure. The data presented here for human serum albumin demonstrate the utility of mass spectrometry in studying protein alterations. This type of information may be helpful in assessing the ability of proteins to act as antioxidants in biological systems which are subject to oxidant stress as in cases of inflammation and in the aging process.