TURNOVER RATES OF HEXOKINASE-I, PHOSPHOFRUCTOKINASE, PYRUVATE-KINASE AND CREATINE-KINASE IN SLOW-TWITCH SOLEUS MUSCLE AND HEART OF THE RABBIT

Hexokinase I was purified from rabbit heart to a specific activity of 70 U/mg protein. The purified enzyme was electrophoretically homogeneous with an apparent molecular weight of 102000. Purified immunoglobulins from sheep were used to titrate the percentage of hexokinase I in various tissues of the rabbit. Precipitating antibodies from sheep were also prepared against rabbit muscle MM‐creatine kinase, phosphofructokinase and pyruvate kinase. Appararent turnover rates of these phosphotransferases and of hexokinase I were determined in rabbit heart and soleus muscle by means of the immunoprecipitation technique after single pulse labelling with [U‐14Cl]leucine in vivo. Apparent half‐lives of phosphofructokinase, pyruvate kinase and hexokinase I were 0.56 d, 0.73 d and 0.93 d in rabbit heart. In slow‐twitch soleus muscle half‐lives of phosphofructokinase, pyruvate kinase, hexokinase I and creatine kinase were 0.63 d, 0.72 d, 0.85 d and 0.82 d. The similarity of the rate constants of degradation of these enzymes is interpreted as an indication that different tissue concentrations result primarily from different rates of synthesis. Copyright © 1979, Wiley Blackwell. All rights reserved