The influence of pH and temperature on the properties of myosin.

1. The rate of denaturation of myosin solutions at temperatures between 32 degrees and 45 degrees and at pH values between 5.3 and 6.2 has been studied, by using adenosine-triphosphatase activity and solubility in m-potassium chloride at pH6.1 as criteria. 2. Myosin, when heated, loses its adenosine-triphosphatase activity before it becomes insoluble. 3. The loss of adenosine-triphosphatase activity and solubility are both first-order and pH-dependent reactions. Myosin, however, becomes insoluble only when heated within a narrow range of pH values. 4. The thermodynamic functions found for the two processes of denaturation are compared and discussed. 5. The possibility is discussed that, in muscle undergoing rigor, conditions may obtain that would denature myosin.