We deal with PTMs such as deamidation (Investigation of asparagine deamidation in a SOD1-based biosynthetic human insulin precursor by MALDI-TOF mass spectrometry), acetylation (Isolation and Characterization of Acetylated Derivative of Recombinant Insulin Lispro Produced in Escherichia coli), formylation, etc.
The identification and localization of PTMs relies on a careful investigation of the MS/MS spectra of peptides derived from the analyzed protein as a result of proteolysis with the use of the dedicated enzyme (e.g. trypsin, Glu-C, Lys-C, Asp-N). The process is carried out based on a database search of protein sequences with the use of the MASCOT® system. Prior to digestion the disulphide bridges in proteins are usually subjected to reduction and alkylation. For the purpose of simulating the spectra fragmentation of the modified peptides we use the GPMAW (Lighthouse data) software.