Tryptic Digestion of Muscle Components Simulates Many of the Changes Caused by Postmortem Storage

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Abstract
The effects of trypsin on subcellular components purified from muscle cells were compared with the effects of postmortem storage on these same components. The results show that: 1) limited trypsin digestion and postmortem storage both cause a small increase in the Ca2+-stimulated, Mg2+-dependent ATPase activity of fragmented sarcoplasmic reticulum; 2) both limited trypsin treatment and postmortem storage cause almost complete loss of the Ca2+-sequestering abilities of fragmented sarcoplasmic reticulum; 3) trypsin treatment and postmortem storage both cause an increase followed by a decrease in the Mg2+-modified ATPase activity of myofibrils; the Ca2+-modified ATPase activity increases and then remains constant during either trypsin treatment or postmortem storage; 4) very brief trypsin digestion and postmortem storage both increase the rate of turbidity development in actomyosin preparations following the addition of ATP; 5) both limited trypsin treatment and postmortem storage cause shortened sarcomeres to lengthen in the absence of ATP; and 6) brief trypsin digestion and postmortem storage both produce degradation of the Z-disk. These striking similarities between the effects of trypsin and the effects of postmortem storage show how proteolysis may be an important factor in postmortem alterations in muscle cells, but they do not prove that proteolysis is actually involved in postmortem muscle alterations. Copyright © 1971. American Society of Animal Science . Copyright 1971 by American Society of Animal Science.

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