The origin of the 30 kDa component appearing during post-mortem ageing of bovine muscle

The most predominant component appearing on SDS-PAGE of myofibrils prepared from bovine m. vastus intermedius (VI) during ageing for 31 days post mortem at 0-2 degrees C was a component with a molecular weight of 32 kDa (SDS-32 kDa). In this study, the origin of the SDS-32 kDa component, which was thought to correspond to the 30 kDa component already known, was investigated. On the SDS-PAGE of the crude troponins, both troponin T and the 34 kDa component were gradually degraded during ageing and then troponin T disappeared at 24 days post mortem, while the concentration of the 32 kDa component showed a tendency to increase during ageing. The 32 kDa component was prepared from troponin of bovine VI muscle stored for 17 days post mortem using CM-Toyopearl chromatography, and named the native 32 kDa component. Its mobility on SDS-PAGE agreed with that of the SDS-32 kDa component. The SDS-32, native 32 and 34 kDa components were recognized by the polyclonal anti-troponin T antibody, and furthermore, the patterns of amino acid composition of both the native 32 and 34 kDa components were very similar to troponin T. Thus, it was considered that these two components would be polypeptides from the degradation of troponin T. We concluded that the SDS-32 kDa component must be derived from the degraded polypeptides of troponin T. However, it still remains a possibility that some degradation products from other myofibrillar proteins are included in the SDS-32 kDa component. Therefore, further studies about the identity of this component will be required.