The inactivation profile of rabbit muscle creatine phosphokinase in tris-acetate buffer solutions.

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Abstract
The inactivation profile of rabbit muscle creatine phosphokinase (CPK) was investigated in Tris-acetate buffer solutions under various conditions of pH and temperature. The inactivation pattern follows apparent 1st-order kinetics at pH very close to 6.00 (isoelectric point of CPK) and 30 to 39.degree. C and at pH 7.40, 39.degree. C. The activation energy of the inactivation at pH very close to 6.00 is 31.8 kcal/mol. The inactivation half-lives of CPK are 13.6 h (pH 5.95, 30.degree. C), 7.9 h (pH 5.93, 35.degree. C), 3.0 h (pH 5.90, 39.degree. C) and 11.9 h (pH 7.40, 39.degree. C). At pH 6.70, the inactivation profile follows a biexponential curve at 30.degree. C and at 39.degree. C. The time course consists of 2 types of inactivation: an initial rapid inactivation (.alpha.-phase) and a gradual inactivation (.beta.-phase). Anomalous irregular inactivation profiles are also observed at pH 7.00, 7.40 and 8.00 at 30.degree. C as well as at pH 8.00 at 39.degree. C. Some possible explanations of these irregular inactivation profiles are presented.