Oxidation of Myofibrillar Proteins and Impaired Functionality: Underlying Mechanisms of the Carbonylation Pathway

The potential impact of protein oxidation on the functional properties of myofibrillar proteins (MP) was investigated in the present study. To accomplish this purpose, myofibrillar proteins were oxidized in vitro for 12 days at 37 degrees C in the presence of Cu2+, Fe3+, and Mb in combination with H2O2 and analyzed at sampling times for chemical changes induced by oxidative reactions and functional properties. The oxidation measurements included specific protein carbonyls (alpha-aminoadipic semialdehyde, AAS), advanced lysine oxidation products (alpha-aminoadipic acid, AAA, and Schiff bases), and thiobarbituric acid-reactive substances (TBARS). The factors and mechanisms involved in the oxidative degradation of lysine residues through the carbonylation pathway are precisely described. According to the present results, intense lipid and protein carbonylation, principally induced by Cu2+/systems, leads to a fast and severe loss of MP functionality, including impaired water-holding, foaming, and gelling capacities. The implication of Mb in the oxidation events enhances the production of AAA and Schiff bases, compromising to a larger extent the solubility of MP and worsening the aggregation and the gelling capacity. The connection between the oxidation-induced chemical changes and the loss of protein functionality is thoroughly discussed.