| Abstract
| - Troponin T (TnT) is one of the myofibrillar proteins that is easily degraded during postmortem agingof pork. In this study, we determined the N-terminal amino acid sequences of TnT degradationfragments produced during postmortem aging and by m-calpain hydrolysis. The N-terminal aminoacid sequences of TnT fragments produced during postmortem aging were EVHEPEEKPRPKLTAP,EKPRPKLTAPKIPEG, and APKIPEGEKVDF. On the other hand, the N-terminal amino acid sequencesof TnT fragments produced by the action of m-calpain were APPPPAEV, EVHEPEEK, and APK.These sequences of degradation fragments could be mapped on fast type TnT isoform 2. The peptide bonds of His37−Glu38 and Thr51−Ala52 in fTnT2 were cleaved during postmortem aging as wellas by the calpain hydrolysis; therefore, calpain was concluded to have an important role in TnTdegradation during postmortem aging. It was also found that the sourness-suppressing peptideAPPPPAEVHEVHEEVH (Okumura et al. Biosci. Biotechnol. Biochem.2004, 68, 1657−1662) derivedfrom TnT degradation could be produced by the action of calpains on Glu21−Ala22 and His37−Glu38sites. Keywords: Troponin T (TnT); postmortem aging; calpain; porcine; degradation; N-terminal amino acidsequence
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