Simultaneous assessment of Asp isomerization and Asn deamidation in recombinant antibodies by LC-MS following incubation at elevated temperatures

PLoS One. 2012;7(1):e30295. doi: 10.1371/journal.pone.0030295. Epub 2012 Jan 17.

Abstract

The degradation of proteins by asparagine deamidation and aspartate isomerization is one of several chemical degradation pathways for recombinant antibodies. In this study, we have identified two solvent accessible degradation sites (light chain aspartate-56 and heavy chain aspartate-99/101) in the complementary-determining regions of a recombinant IgG1 antibody susceptible to isomerization under elevated temperature conditions. For both hot-spots, the degree of isomerization was found to be significantly higher than the deamidation of asparagine-(387, 392, 393) in the conserved CH3 region, which has been identified as being solvent accessible and sensitive to chemical degradation in previous studies. In order to reduce the time for simultaneous identification and functional evaluation of potential asparagine deamidation and aspartate isomerization sites, a test system employing accelerated temperature conditions and proteolytic peptide mapping combined with quantitative UPLC-MS was developed. This method occupies the formulation buffer system histidine/HCl (20 mM; pH 6.0) for denaturation/reduction/digestion and eliminates the alkylation step. The achieved degree of asparagine deamidation and aspartate isomerization was adequate to identify the functional consequence by binding studies. In summary, the here presented approach greatly facilitates the evaluation of fermentation, purification, formulation, and storage conditions on antibody asparagine deamidation and aspartate isomerization by monitoring susceptible marker peptides located in the complementary-determining regions of recombinant antibodies.

MeSH terms

  • Amides / chemistry
  • Amides / metabolism
  • Amino Acid Sequence
  • Animals
  • Antibodies / chemistry
  • Antibodies / genetics
  • Antibodies / metabolism*
  • Asparagine / chemistry
  • Asparagine / metabolism*
  • Aspartic Acid / chemistry
  • Aspartic Acid / metabolism*
  • CHO Cells
  • Chromatography, Liquid / methods*
  • Complementarity Determining Regions / chemistry
  • Complementarity Determining Regions / genetics
  • Complementarity Determining Regions / metabolism
  • Cricetinae
  • Cricetulus
  • Hydrogen-Ion Concentration
  • Immunoglobulin G / chemistry
  • Immunoglobulin G / genetics
  • Immunoglobulin G / metabolism
  • Isomerism
  • Mass Spectrometry / methods*
  • Protein Binding
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Surface Plasmon Resonance
  • Temperature

Substances

  • Amides
  • Antibodies
  • Complementarity Determining Regions
  • Immunoglobulin G
  • Recombinant Proteins
  • Aspartic Acid
  • Asparagine