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The effect of post‐mortem conditions on the extractability and adenosine triphosphatase activity of myofibrillar proteins of rabbit muscle
Author(s) -
PENNY I. F.
Publication year - 1967
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/j.1365-2621.1967.tb01356.x
Subject(s) - adenosine triphosphatase , myofibril , triphosphatase , myosin , chemistry , adenosine , sodium , actin , biophysics , atpase , kinetics , biochemistry , enzyme , biology , organic chemistry , quantum mechanics , physics
Summary. 1. Washed myofibrils from rabbit muscle have been heated at pH values between 4.8 and 5.6 and temperatures between 35°C and 42°C. It has been found that, under these conditions, myofibrils lose their Ca 2+ activated adenosine triphosphatase, their Mg 2+ activated adenosine triphosphatase and also become less extractable in M KCl–30 mM sodium glycerophosphate, pH 6.2. 2. The reactions follow first‐order kinetics and the rates are dependent on pH and temperature. The first order rate constants, enthalpies and entropies for the three reactions are sufficiently near each other to suggest that all three reactions are occurring simultaneously. 3. When a muscle is allowed to go into rigor at 37°C the extractability in M KCl–30 mM sodium glycerophosphate is reduced after 4 hr at 37°C when the pH of the muscle has reached 5.55. At the same time the Ca 2+ adenosine triphosphatase activity falls but the Mg 2+ adenosine triphosphatase does not. The latter is reduced by prolonging the period at 37°C to 6 hr. 4. It is suggested that there is present in muscle, undergoing rigor at 37°C, myosin which does not bind to actin and is readily denatured. When bound to actin, myosin in the myofibril is more resistant and denatures only after long exposure to a temperature of 37°C.