Abstract
In this study, we explored the MS/MS behavior of various synthetic peptides that possess a lysine residue at the N-terminal position. These peptides were designed to mimic peptides produced upon proteolysis by the Lys-N enzyme, a metalloendopeptidase issued from a Japanese fungus Grifola Frondosa that was recently investigated in proteomic studies as an alternative to trypsin digestion since a specific cleavage at the amide X-Lys chain is obtained providing N-terminal lysine peptide fragments. In contrast to tryptic peptides exhibiting a In lysine or arginine residues solely at the C-terminal position, and thus devoid of such basic amino acids within the sequence, these Lys-N proteolytic peptides can contain the highly basic arginine residue anywhere within the peptide chain. The fragmentation patterns of such sequences with ESI-QqTof and MALDI-Tof/Tof mass spectrometers commonly used in proteomic bottom-up experiments were investigated.