μ-Calpain oxidation and proteolytic changes on myofibrillar proteins from Coregonus Peled in vitro.

The purpose of this study was to investigate the structural properties of μ-calpain induced by hydroxyl radical oxidation and its effect on the degradation of myofibrillar protein (MP) from the dorsal muscles of Coregonus peled. The carbonyl and sulfhydryl content of μ-calpain changed significantly after oxidation. The content of α-helix in the secondary structure decreased from 0.825 to 0.232 and the changes in intrinsic fluorescence and ultraviolet (UV) absorption spectra indicated that oxidation could cause the expansion and aggregation of µ-calpain molecules. Changes in µ-calpain structure could improve the activity of µ-calpain, reaching the highest value at 0.5 mM H2O2. The highest µ-calpain activity facilitate the degradation of unoxidized MP, while the degradation of oxidized MP was facilitated at the 1 mM H2O2. Thus, our results provide a scientific basis for the interaction mechanism among hydroxyl radical oxidation, µ-calpain, and MP degradation.