Post-translational modifications and antioxidant properties of different therapeutic human serum albumins

Human serum albumin (HSA) is widely used for the treatment of diverse clinical conditions to restore plasma volume, manage burns and treat hypoproteinemia.Although the HSA preparations should ideally preserve its functionality, the structural integrity and antioxidant properties of HSA may be compromised as a result of the manufacturing process. The present study examined seven commercially available HSA preparations for clinical use to investigate their post-translational modifications (PTMs) and antioxidant activity, including DPPH radical-scavenging, peroxyl radical antioxidant and metal binding activities, by means of mass spectrometry and Ellman's assay. The results confirmed that most of the PTMs of HSA and especially the oxidation of the free thiol residue varied between the different commercial albumins and the percentage of these PTMs were higher than those of physiological HSA. Moreover, HSA-DA isoform was increased at the end of the stability time and new oxidative modifications occurred in these samples. In conclusion, the bioprocesses for production of commercial albumins are responsible of their wide heterogeneity, being the ethanol fractionation and their storage conditions the more critical phases. Nonetheless, the Kedrion albumin shows a high content of free thiol and a lower concentration of PTMs than other commercial albumins.