Mechanism of production of troponin T fragments during postmortem aging of porcine muscle.
Troponin T (TnT) is one of the myofibrillar proteins that is easily degraded during postmortem aging of pork. In this study, we determined the N-terminal amino acid sequences of TnT degradation fragments produced during postmortem aging and by m-calpain hydrolysis. The N-terminal amino acid sequences of TnT fragments produced during postmortem aging were EVHEPEEKPRPKLTAP, EKPRPKLTAPKIPEG, and APKIPEGEKVDF. On the other hand, the N-terminal amino acid sequences of 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 well as by the calpain hydrolysis; therefore, calpain was concluded to have an important role in TnT degradation during postmortem aging. It was also found that the sourness-suppressing peptide APPPPAEVHEVHEEVH (Okumura et al. Biosci. Biotechnol. Biochem. 2004, 68, 1657-1662) derived from TnT degradation could be produced by the action of calpains on Glu21-Ala22 and His37-Glu38 sites.
Kitamura
Shin-ichi
S
Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima 739-8528, Japan.
Muroya
Susumu
S
Tanabe
Soichi
S
Okumura
Tomoyuki
T
Chikuni
Koichi
K
Nishimura
Toshihide
T
D000595:Amino Acid Sequence; D000818:Animals; D002154:Calpain / Q000378:metabolism; D006868:Hydrolysis; D008460:Meat; D008969:Molecular Sequence Data; D009132:Muscles / Q000737:chemistry* / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011180:Postmortem Changes; D013552:Swine; D013997:Time Factors; D020107:Troponin T / Q000737:chemistry* / Q000378:metabolism*
D010446:Peptide Fragments; D020107:Troponin T; D002154:Calpain