Hydroxyl radical oxidation destabilizes subfragment-1 but not the rod of myosin in chicken myofibrils

The thermal denaturation process of myosin in oxidized chicken myofibrils was investigated. Exposures of myofibrils to hydroxyl radical-generation systems (HRGS) resulted in an enhanced susceptibility of myosin to thermal inactivation of Ca-ATPase and a loss of salt solubility. The chymotryptic production of subfragment-1 (S-1) from myosin in oxidized myofibrils decreased more rapidly than that in un-oxidized myofibrils upon heating, which paralleled the Ca-ATPase decay. However, the heat-induced decrease in chymotryptic production of rod from myosin was not affected by the HRGS treatment. The results suggested that free radical oxidation promoted thermal destabilization of myosin in the S-1 portion instead of the rod portion. The altered myosin denaturation pattern due to hydroxyl radical oxidation was likely a cause for functionality changes in oxidatively stressed myofibrillar proteins in meat processing.