title: Sensitive and site-specific identification of carboxymethylated and carboxyethylated peptides in tryptic digests of proteins and human plasma.
abstract: Glycation refers to a nonenzymatic post-translational modification formed by the reaction of amino groups and reducing sugars. Consecutive oxidation and degradation can produce advanced glycation end products (AGEs), such as N(ε)-(carboxyethyl)lysine (CEL) and N(ε)-(carboxymethyl)lysine (CML). Although CEL and CML are considered to be markers of arteriosclerosis, diabetes mellitus, and aging, the modified proteins and the exact modification sites are mostly unknown due to their low frequency and a lack of enrichment strategies. Here, we report characteristic fragmentation patterns of CML- and CEL-containing peptides and two modification-specific reporter ions for each modification (CML, m/z 142.1 and 187.1; CEL, m/z 156.1 and 201.1). The protocol allowed sensitive and selective precursor ion scans to detect the modified peptides in complex sample mixtures. The corresponding m/z values identified eight CEL/CML-modification sites in glycated human serum albumin (HSA) by targeted nano-RPC-MS/MS. The same strategy revealed 21 CML sites in 17 different proteins, including modified lysine residues 88 and 396 of human serum albumin, in a pooled plasma sample that was obtained from patients with type 2 diabetes mellitus.
authors.affiliation: Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, ‡Center for Biotechnology and Biomedicine (BBZ), §Institute of Organic Chemistry, Faculty of Chemistry and Mineralogy, Universität Leipzig , 04103 Leipzig, Germany.
authors.forename: Uta
authors.initials: U
authors.lastname: Greifenhagen
authors.forename: Viet Duc
authors.initials: VD
authors.lastname: Nguyen
authors.forename: Johann
authors.initials: J
authors.lastname: Moschner
authors.forename: Athanassios
authors.initials: A
authors.lastname: Giannis
authors.forename: Andrej
authors.initials: A
authors.lastname: Frolov
authors.forename: Ralf
authors.initials: R
authors.lastname: Hoffmann
mesh_terms: D000595:Amino Acid Sequence; D001798:Blood Proteins / Q000737:chemistry*; D017127:Glycation End Products, Advanced / Q000737:chemistry; D006801:Humans; D008745:Methylation; D010455:Peptides / Q000737:chemistry*; D053719:Tandem Mass Spectrometry; D014357:Trypsin / Q000737:chemistry*
chemical_list: D001798:Blood Proteins; D017127:Glycation End Products, Advanced; D010455:Peptides; D014357:Trypsin
keywords: AGEs; CEL; CML; glycation; precursor ion scan; tandem mass spectrometry