Mild oxidation promotes myosin S2 cross-linking by microbial transglutaminase

The cross-linking of myosin, an important property in meat processing, has previously been studied in complex myofibril systems to address free radical and microbial transglutaminase (MTG) effects. In the present study, purified myosin from pork Longissimus muscle was modified with H2O2 and 10 mu M Fe to determine the effects of oxidation on the subsequent cross-linking by MTG (E:S = 1:20) at 4 degrees C. When subjected to MTG, the degree of cross-linking in mildly oxidized myosin sample (1mM H2O2) reached 87.6%, compared to 64.7% in MTG-treated nonoxidized myosin and 33.8% in excessively oxidized myosin (200 mM H2O2), based on the epsilon(gamma-glutamyl)lysine bond, SDS-PAGE, and solubility analyses. Although S1 in myosin was always the principal cross-linking site, the S2 subfragment became a significant new region of cross-linking when stressed by 1mM H2O2. These findings may guide the MTG application in meat processing where oxidation is not inhibited.