Mass spectrometric analysis of asparagine deamidation and aspartate isomerization in polypeptides

Electrophoresis. 2010 Jun;31(11):1764-72. doi: 10.1002/elps.201000027.


One of the most frequent modifications in proteins and peptides is the deamidation of asparagine, a spontaneous non-enzymatic reaction leading to a mixture of L,D-succinimidyl, L,D-aspartyl, and L,D-isoaspartyl forms, with L-isoaspartyl dominating. Spontaneous isomerization of L-Asp yields the same products. In vivo, these unusual forms of aspartate are repaired by the protein L-isoaspartyl O-methyltransferase enzyme, with the balance between isomerization and repair affecting the organism physiology. Mass spectrometric analysis of this balance involves isomer separation, iso-Asp/Asp quantification, and iso-Asp site identification. This review highlights the issues associated with these steps and discusses the prospects of high-throughput iso-Asp analysis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amides / chemistry*
  • Amides / metabolism
  • Animals
  • Asparagine / chemistry*
  • Asparagine / metabolism
  • Aspartic Acid / chemistry*
  • Aspartic Acid / metabolism
  • Electrophoresis, Gel, Two-Dimensional
  • Humans
  • Isomerism
  • Mass Spectrometry / methods*
  • Mice
  • Proteomics / methods*


  • Amides
  • Aspartic Acid
  • Asparagine