| Autor: |
Camou, J. P., Marchello, J. A., Thompson, V. F., Mares, S. W., Goll, D. E. |
| Předmět: |
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| Zdroj: |
Journal of Animal Science; Oct2007, Vol. 85 Issue 10, p2670-2681, 12p, 4 Diagrams, 4 Graphs |
| Abstrakt: |
An in situ system involving incubation of 60- to 80-g pieces of muscle at 4°C under different conditions was used to determine the effects of time of postmortem storage, of pH, and of temperature on activities of μ- and m-calpain activity in bovine skeletal muscle. Casein zymograms were used to allow measurement of calpain activity with a minimum of sample preparation and to ensure that the calpains were not exposed to ionic strengths of 100 or greater before assay of their activities. In 4 of the 5 muscles (longissimus dorsi, lumbar; longissimus dorsi, thoracic; psoas major; semimembranosus; and triceps brachii) studied, μ-calpain activity decreased nearly to zero within 48 h post-mortem. Activity of m-calpain also decreased in the in situ system used but at a much slower rate. Activities of both μ- and m-calpain decreased more slowly in the triceps brachii muscle than in the other 4 muscles during postmortem storage. Although previous studies have indicated that μ-calpain but not m-calpain is proteolytically active at pH 5.8, these studies have used calpains obtained from muscle at death. Both μ- and m-calpain are proteolytically inactive if their activities are measured at pH 5.8 and after incubating the muscle pieces for 24 h at pH 5.8. Western analysis suggested that neither the large 80-kDa subunit nor the small 28-kDa subunit of m-calpain was autolyzed during post-mortem storage of the muscle pieces. As has been reported previously, the 80-kDa subunit of μ-calpain was autolyzed to 78- and then to a 76-kDa polypeptide after 7 d postmortem, but the 28-kDa small subunit was not autolyzed; hence, the autolyzed μ-calpain molecule in postmortem muscle is a 76-/28-kDa molecule and not a 76-/18-kDa molecule as previously assumed. Because both subunits were present in the postmortem calpains, loss of μ-calpain activity during postmortem storage is not due to dissociation of the 2 subunits and inactivation. Although previous studies have shown that the 76-/18-kDa μ-calpain molecule is completely active proteolytically, it is possible that the 76-/28-kDa μ-calpain molecule in postmortem muscle is proteolytically inactive and that this accounts for the loss of μ-calpain activity during postmortem storage. Because neither μ- nor m-calpain is proteolytically active at pH 5.8 after being incubated at pH 5.8 for 24 h, other proteolytic systems such as the caspases may contribute to post-mortem proteolysis in addition to the calpains. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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