RESUMO
In this study, we examined for the first time the effect of the HOCl/OCl-- and H2O2-induced oxidation of Glu-plasminogen on damage to its primary structure and the biological activity of plasmin. The consolidated results obtained with the aid of MS/MS, electrophoresis, and colourimetry, demonstrated that none of the oxidised amino acid residues found in the proenzyme treated with 25 µM HOCl/OCl- or 100 µM H2O2 were functionally significant for plasminogen. However, the treatment of plasminogen with increasing concentrations of HOCl/OCl- from 25 µM to 100 µM or H2O2 from 100 µM to 300 µM promoted a partial loss in the activity of oxidised plasmin. Several methionine residues (Met57, Met182, Met385, Met404, Met585, and Met788) localized in different protein domains have been shown to serve as ROS traps, thus providing an efficient defense mechanism against oxidative stress. Oxidised Trp235, Trp417, Trp427, Trp761, and Tyr672 are most likely responsible for the reduced biological activity of Glu-plasminogen subjected to strong oxidation. The results of the present study, along with those of previous studies, indicate that the structure of Glu-plasminogen is adapted to oxidation to withstand oxidative stress induced by ROS.
