Glycation induced modification and identification of AGEs-precursors and AGEs in human serum albumin

AGEs are a heterogeneous group of proteins that have been shown to react with the amino group of the N-terminal amino acid residue and the side-chains of arginine and lysine residues. Glycation induced protein modifications has been implicated in diabetes and its associated complications like nephropathy, retinopathy, aging as well as in atherosclerosis, Alzheimer's and Parkinson's diseases. The identification and structure elucidation of AGEs is therefore of great importance. Mass spectrometry, due to its high specificity and sensitivity, has widely been applied for the identification and structure elucidation of AGEs. We report the identification of AGEs-precursors and AGEs based on relative mass changes due to specific AGEs formation. HPLC-ESIMS, ESI-MS/MS and mascot data base were used to identify peptides sequence for non-glycated HSA. The relative mass changes due to specific AGE-precursors and AGEs formation were added to the non-glycated peptides followed by a thorough manual search of the glycated samples that resulted in the identification of ten modified peptides for the formation of five AGEs namely CML (1), Pyrraline (3), Imidazolone A (2), Imidazolone B (1) and AFGP (3). Also, seven glycated peptides were identified for the formation of AGEs-precursors.