1P-08 PDF
化学修飾トリプシンの不都合な真実
Chemically modified trypsin by reductive methylation is a standard reagent in protein identification by mass spectrometry. The reductive methylation of trypsin is supposed to protect the enzyme against autolysis. However, it has been reported that peptides with mono- or di-methylated Lys, or Asn residue, at their C-termini were observed in autolysis products of chemically modified trypsin. Usually, the chemical modification of trypsin is not considered in database searches. Modified trypsin-derived spectral data might be incorrectly assigned to peptides of other proteins, making false-positive identification. In this paper, autolysis products of chemically modified trypsins available from commercial sources were scrutinized by nanoLC/ESI-MS/MS. We will report details of sequences and modifications of the autolysis products, those are inconvenient truths for proteomics scientists.