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KMID : 0366319920120030183
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Biochemistry and Molecular Biology News
1992 Volume.12 No. 3 p.183 ~ p.187
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Abstract
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The reaction mechanism of calcium ion in the post-mortem weakening of Z-disks was studied in myofibrils prepared from fresh or stored muscles. The a-actinin showing very limited proteolysis of myofibrils during postmortem storage of muscles at 10 . The postmortem weakening of Z-disks was markedly dependent on muscle pH, showing a minimum at pH 6.5. These results agree well with calcium-induced weakening of Z-disks of freshly isolated myofibrils, indicating that no protease participates in the postmortem weakening of Z-disks.
Z-disks of myofibrils prepared from stored muscles
split into halves after treatment with O.1N NaOH for 5 min. The identical splitting of Z-disks was induced by a calcium ion concentration of 10-4 M, which is of the same order of magnitude as that in the sarcoplasm in postmortem muscle. We therfore conclude that the postmortem weakening of Z-disks is non-enzymatically induced by the raised sarcoplasmic calcium ion concentration of 10-4 M. Calcium ions probably solubilize the amorphous cementing material of Z-disks,leaving unchainged the two sets of Z-filaments composed of a-actinin.
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