P 148 - Identification of novel carbonylated amino acids in proteins from human plasma

Abstract

In order to fully understand the role of protein carbonylation in health and disease, identification of carbonylated protein(s), and their detailed characterisation is required. Mass spectrometry is a particularly suited for such studies due to its specificity and sensitivity. We have used biotin-hydrazide and mass spectrometry based approach for identification of up to 14 different types of carbonylated amino acids. In native human plasma we have observed 133 carbonylated sites in 36 proteins. The approach identified 10 hitherto undetected types of carbonylated amino acids in proteins: aldehyde and ketone modifications of leucine, valine, alanine, isoleucine, glutamine, lysine and glutamic acid (+14 Da), an oxidised form of methionine - aspartate semialdehyde (-32 Da) - and decarboxylated glutamic acid and aspartic acid (-30 Da). The carbonyl compounds reported are consistent with the chemistry of peroxyl and alkoxyl radicals generated on proteins. The consequence of the formation of these products has yet to be understood. However, it is important to note that some of these carbonyls can introduce changes to protein charge, give rise to Schiff base cross-links, and can lead to changes in residues that define protein structure (e.g. ring opening of P residues). These events may affect protein function (e.g. interaction with other) or protein conformation and activity.