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

Abstract

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 to 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 °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.

Pseudo-enzymatic hydrolysis of 4-nitrophenyl acetate by human serum albumin: pH-dependence of rates of individual steps

“…(iv) The ionization state of Tyr411 modulates NphOAc hydrolysis; indeed substrate binding to HSA induces the acidic pK a shift of the Tyr411 residue. (v) HSA acylation appears relevant from the pharmacokinetic viewpoint; indeed HSA acylation by aspirin [23], beside increasing the affinity of phenylbutazone and inhibiting bilirubin binding, reduces prostaglandin affinity, accelerating the clearance of prostaglandins and serving as an additional mechanism of the aspirin anti-inflammatory effect [24].…”

Metabolic Mechanism of Delamanid, a New Anti-Tuberculosis Drug, in Human Plasma

“…Moreover, using selective amino acid reagents, these authors concluded that Cys, Trp, Arg, and Tyr participate in the carbarylase activity of HSA (Sogorb et al, 2004). Finally, it was reported that the bioconversion of aspirin by albumin is a pseudo-esterase reaction in which aspirin stably acetylates lysines on albumin and releases salicylate (Liyasova et al, 2010). These reports collectively suggest that amino acid residues, such as lysine, tryptophan, and arginine, phenolic hydroxyl groups, such as tyrosine, and thiol groups, such as cysteine in HSA, may be involved in the first step of delamanid metabolism by albumin.…”

“…Albumin, the most abundant protein in plasma (Theodore, 1996), displays pseudo-enzymatic properties and has been found to catalyze the hydrolysis of numerous compounds, such as cinnamoyl imidazole (Ohta et al, 1983), p-nitrophenyl esters (Means and Bender, 1975;Kurono et al, 1979;Watanabe et al, 2000;Sakurai et al, 2004;Lockridge et al, 2008), olmesartan medoxomil (Ma et al, 2005), carbaryl (Sogorb et al, 2004), aspirin (Rainsford et al, 1980;Liyasova et al, 2010), organophosphate insecticides (Sultatos et al, 1984), and Fig. 8.…”

Quantitative Profiling of Post-translational Modifications by Immunoaffinity Enrichment and LC-MS/MS in Cancer Serum without Immunodepletion

“…Currently, there exists very limited data about PTMs in serum/plasma beyond glycosylation. The abundant serum protein albumin has long been known to be acetylated by aspirin, and this reaction can occur in vitro without the presence of any acetyltransferase (9). Fibrinogen, another abundant serum protein, is also acetylated by aspirin both in vivo and in vitro (10,11).…”