Influence of oxidation on myofibrillar proteins degradation from bovine via μ-calpain

The objective of this study was to investigate the effect of oxidation on proteolysis of myofibrillar proteins via μ-calpain. Myofibrillar proteins prepared from bovine muscle were exposed to in vitro oxidation to produce varying levels of protein modification by use of H2O2 and Fe2+. The protein oxidation level was measured by the carbonyl content. Modified proteins were then incubated with active μ-calpain and the rates of protein degradation were analyzed via SDS–PAGE and western blotting. The results revealed that increased protein oxidation enhanced the degradation of myosin heavy chain (MHC) and α-actinin, reduced the degradation of 38 kDa troponin-T, but had little influence on the 30 kDa degradation fragment derived from troponin-T and the degradation of actin. These findings demonstrated that the oxidative modification of myofibrillar proteins changed their susceptibility to μ-calpain and provided a mechanistic link connecting oxidation with myofibrillar proteolysis.