Protein glycation is a spontaneous PTM of the proteome focused mainly on N-terminal and lysine side chain amino groups by glucose forming fructosa- mine residues and on guanidino groups of arginine residues forming mainly MG-derived hydroimidazolone residues. The latter appears to be most functionally damaging in physiological systems. Glycation is a relatively labile PTM, and so customized preanalytical processing is required to avoid compromising mass spectrometric analysis outcomes. ETD fragmentation has a clear advantage for the analysis of the fructosamine proteome, whereas CID, HCD, and ETD may be used for arginine-based dihydroxyimidazolidine/hydroimi- dazolone detection. Robust procedures are available for the detection and quantitation of total glycation adducts in protein extracts, and these may be combined with proteomics analysis for added security of findings - particularly as it is still challenging to achieve high sequence coverage in proteomics experiments. LC-MS/MS quantitative analysis of glycated proteins by MRM of glycated tryptic peptides may provide valuable diagnostic markers where functional impairment is linked to disease, for example, proatherogenicity of MG-modified apolipoprotein B100 in MG-modified low-density lipoprotein . Bioinformatics tools for the analysis of protein glycation sites are in development and will help surety of detection and identification of functionally and physiologically important proteome modifications by glycation.
We thank the Biotechnology and Biological Sciences Research Council, European Union FP7 program, and British Heart Foundation for the support for our glycation research.