This document summarizes a PhD dissertation that studied the effect of calcium, ATP, and nitrite on the degradation of myofibrillar proteins by lysosomal enzymes. It found that the addition of calcium, ATP, or a mixture stimulated the degradation of myofibrillar connection, myosin, and other proteins. Calcium or ATP enhanced lysosomal protease activity and protein degradation. Sodium nitrite decreased chicken protein degradation but had little effect when calcium and ATP were present. The combination of lysosomal enzymes, calcium, and ATP degraded various chicken muscle proteins. Calcium, ATP, or their mixture enhanced the water-holding capacity of beef proteins during degradation.

1. EFFECT OF CALCIUM, ADENOSINE TRIPHOSPHATE, AND NITRITE ON
THE DEGRADATION OF MYOFIBRILLAR PROTEIN (ATP)
Yousef Mohamed Elshrek
PhD Dissertation University of Missouri - Columbia 179 (1982)
Beef and chicken myofibrils were used as substrates to study the effect of CaCl2, ATP, and
beef muscle lysosomal enzymes on protein degradation. Degradation of beef and chicken
myofibrillar proteins was measured using sodium dodecyl sulfate-polyacrylamide gel
electrophoresis (SDS-PAGE), water holding capacity (WHC), and nonprotein nitrogen
(NPN). The reactions were carried out at pH 5.5 and 7.0 at 4(DEGREES)C and
37(DEGREES)C for 1.5, 6, 24, 48, and 96 h. The addition of CaCl2, ATP, or a mixture of
CaCl2 and ATP to prerigor myofibrils stimulated degradation of connection, myosin,
M(,(alpha)) and M(,(beta)) proteins. CaCl2 or ATP or a mixture of the two enhanced
lysosomal protease activity at pH 5.5 and 7.0 and stimulated degradation of M(,(alpha))
and M(,(beta)) proteins. pH optima of beef lysosomal enzymes were found at pH 7.0 and
5.0. Activity at pH 5.0 was 50% of that at pH 7.0. One mM CaCl2 , 5 mM ATP, 5 mM ADP,
or 5 mM AMP enhanced the proteolysis of the chicken myofibrillar proteins, actomyosin,
and connectin, while sodium nitrite decreased degradation of chicken myofibrillar proteins
at pH 7.0, 37(DEGREES)C. Sodium nitrite (NaNO2) had little influence on enzyme activity
in the presence of CaCl2 and/or ATP. Dilute salt-soluble chicken breast myofibrillar
proteins treated with NaNO2 were completely degraded by lysosomal enzymes containing
ATP and by a reaction mixture containing lysosomal enzymes, ATP and CaCl2 Troponin T,
troponin C, and myosin light chains in the same sample were degraded by all treatments
containing lysosomal enzymes, CaCl2 and ATP. The influence of CaCl(,2), ATP, and
lysosomal enzymes independently and in combination on the water-holding capacity
(WHC) of beef myofibrillar proteins was also studied. WHC of beef myofibrils reacted with
lysosomal enzymes was enhanced by adding ATP, CaCl2 , or a mixture of the two, but was
reduced in the presence of CaCl2 alone.
Keywords: Biological science, Food science
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