Reaction of human albumin with aspirin in vitro: mass spectrometric identification of acetylated lysines 199, 402, 519, and 545

Biochem Pharmacol. 2010 Mar 1;79(5):784-91. doi: 10.1016/j.bcp.2009.10.007. Epub 2009 Oct 27.


The aspirin esterase activity of human plasma is due to butyrylcholinesterase and albumin. Our goal was to identify the amino acid residues involved in the aspirin esterase activity of albumin. Fatty acid-free human albumin and human plasma were treated with aspirin for 5 min-24 h. Acetylated residues were identified by LC/MS/MS and MALDI-TOF/TOF mass spectrometry of tryptic peptides. Treatment with 0.3 mM aspirin resulted in acetylation of Lys-199, Lys-402, Lys-519, and Lys-545. Treatment with 20 mM aspirin resulted in acetylation of 26 lysines. There was no acetylation of Tyr-411, under any conditions. Acetylated lysine was stable for at least 21 days at pH 7.4, 37 degrees C. Albumin acetylated by aspirin had reduced esterase activity with beta-naphthyl acetate as shown on gels stained for esterase activity. It was concluded that the aspirin esterase activity of albumin is a pseudo-esterase activity in which aspirin stably acetylates lysines and releases salicylate.

Publication types

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

MeSH terms

  • Acetylation
  • Aspirin / chemistry*
  • Aspirin / pharmacology
  • Carboxylic Ester Hydrolases / chemistry
  • Chromatography, High Pressure Liquid
  • Humans
  • In Vitro Techniques
  • Lysine / chemistry*
  • Lysine / drug effects
  • Models, Molecular
  • Peptide Mapping
  • Serum Albumin / chemistry*
  • Serum Albumin / drug effects
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods*
  • Tandem Mass Spectrometry


  • Serum Albumin
  • Carboxylic Ester Hydrolases
  • acetylsalicylic acid hydrolase
  • Lysine
  • Aspirin