A method for the detection of asparagine deamidation and aspartate isomerization of proteins by MALDI/TOF-mass spectrometry using endoproteinase Asp-N

Daisuke Kameoka, Tadashi Ueda, Taiji Imoto

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A method was established for evaluating Asn deamidation and Asp isomerization/racemization. To detect the subtle changes in mass that accompany these chemical modifications, we used a combination of enzyme digestion by endoproteinase Asp-N, which selectively cleaves the N-terminus of L-α-Asp, and MALDI/TOF-mass spectrometry. To achieve better resolution, we employed digests of 15N-labeled protein as an internal standard. To demonstrate the advantages of this method, we applied it to identify deamidated sites in mutant lysozymes in which the Asn residue is mutated to Asp. We also identified the deamidation or isomerization site of the lysozyme samples after incubating them under acidic or basic conditions.

Original languageEnglish
Pages (from-to)129-135
Number of pages7
JournalJournal of Biochemistry
Issue number1
Publication statusPublished - Jul 1 2003


All Science Journal Classification (ASJC) codes

  • Medicine(all)
  • Biochemistry
  • Molecular Biology

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