Preparation and Properties of Trout Myosin

Abstract

Myosin from the white, dorsal muscle of trout was isolated by a modification of the method of Mackie and Connell (1964). This myosin was homogeneous in the ultracentrifuge at 5 C. The corrected sedimentation coefficient, S°20,w = 6.50, was similar to those for cod and rabbit myosin. The isolated protein had two enzymatic activities, an adenosine triphosphatase (ATPase) and an acetylcholinesterase. The rate of inactivation of the acetylcholinesterase activity at 45 C was approximately equal to the rate of inactivation of the ATPase activity at 25 C. Inactivation of the ATPase was a first-order process with respect to time and 0.6th order with respect to protein concentration. The energy of activation was 46 kcal mole−1 at pH 6.8, lower than values reported for rabbit myosin. Using the loss of enzyme activity as a measure of denaturation, trout myosin was about 23 × more stable than cod myosin, but lost its activity about 25 × more rapidly than rabbit myosin. Some of the mechanisms active in denaturing myosin are briefly discussed.