Actions of cathepsins on troponin T during postmortem aging of porcine muscle

In this study, we examined the contribution of the cathepsins (cathepsin D and crude cathepsins containing cathepsins B and L) to troponin T degradation during postmortem aging. The action of cathepsin D on troponin T was examined at various pHs (pH 4.0-6.5). The degradation of intact troponin T was observed at pH 4.0, but not observed at pH 5.5 and 6.5. As a result of the degradation of troponin T, the 30 kDa fragment was not generated in any pH condition. The action of the crude cathepsins on troponin T was also examined at various pHs (pH 4.0-6.5). The intact troponin T was degraded at pH 4.0 and the 30 kDa fragments were observed. These 30 kDa fragments disappeared during further incubation. On the other hand, at pH 5.5 and 6.5, the intact troponin T was degraded and the 30 kDa fragment was accumulated. These results suggested that the cathepsin D scarcely contributed to the degradation of troponin T during postmortem aging, but crude cathepsins containing cathepsins B and L were partially involved in the degradation of troponin T and the generation of 30 kDa fragments.