1. 1. Heparin stimulates the activity of nonactivated and activated skeletal muscle phosphorylase kinase in a Ca2+-dependent manner. 2. 2. The stimulatory effect of heparin on the activity of nonactivated phosphorylase kinase is also expressed in the presence of calmodulin and glycogen. Heparin acted in synergism with glycogen. 3. 3. Heparin increases the affinity of phosphorylase kinase to Ca2+ 5-12 fold depending upon the activation conditions. 4. 4. Ca2+ influences the stimulation of liver phosphorylase kinase by heparin in a similar way.
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