title: Liberation of phospholipids from Z-disks of chicken skeletal muscle myofibrils by 0.1 mM calcium ions: weakening mechanism for Z-disks during post-mortem aging of meat.
abstract: Weakening of the Z-disks of skeletal muscle myofibrils contributes to the tenderization of meat during post-mortem aging. To elucidate the weakening mechanism, we compared Z-disks weakened by post-mortem aging of chicken breast muscle with those of myofibrils treated with a solution containing 0.1 mM CaCl2 and 1 microM calpastatin domain I. In both cases, the Z-disks were weakened with a corresponding liberation of their constituent phospholipids (PLs). The liberation of PLs specific to 0.1 mM calcium ions was minimal at pH 6.5 and maximal at 35 degrees C together with the Z-disk weakening. Binding of calcium ions to PLs in the Z-disks was determined by 45Ca-autoradiography. Acidic PLs were strongly radioactive and neutral PLs were appreciably radioactive. It is very probable that acidic PLs would bind electrostatically to alpha-actinin under physiological conditions, and that this interaction would be broken by the binding of calcium ions at 0.1 mM to PLs, resulting in the partial liberation of PLs from Z-disks. We conclude, therefore, that the liberation of PLs by the binding of 0.1 mM calcium ions was the main cause for Z-disk weakening during the post-mortem aging of chicken.
authors.affiliation: Department of Animal Science, Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Shimada
authors.forename: D H
authors.initials: DH
authors.lastname: Ahn
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002645:Chickens; D008460:Meat; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism*; D009210:Myofibrils / Q000187:drug effects* / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D011180:Postmortem Changes
chemical_list: D010743:Phospholipids; D002118:Calcium