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Regulation of glycogen phosphorylase and glycogen synthase ec 2.4.1.11 by adrenaline in soleus muscle of phosphorylase kinase ec 2.7.1.38 deficient mice


European Journal of Biochemistry 115(3): 619-626
Regulation of glycogen phosphorylase and glycogen synthase ec 2.4.1.11 by adrenaline in soleus muscle of phosphorylase kinase ec 2.7.1.38 deficient mice
Mixed skeletal muscles of ICR/IAn mice contain 0.2% of the phosphorylase kinase activity found in C3H/He-mg mice at pH 8.2 in the presence of Ca2+. This lack of activity is caused by the absence of the normal phosphorylase kinase protein. The trace residual activity in ICR/IAn mice has quite different properties from the normal enzyme. It has a much higher activity ratio (pH 6.8/8.2), its activity is less dependent on Ca2+, and it is not activated by cAMP-dependent protein kinase or by trypsin. Its elution behavior on Sepharose 4B differs from the normal enzyme. A consequence of the higher activity ratio (pH 6.8/8.2) and decreased effect of Ca2+ is that mixed skeletal muscles of ICR/IAn mice contain 7% of normal activity at pH 6.8 in the absence of Ca2+. The activity of phosphorylase kinase in C3H/He-mg control mice is 6-fold lower in red oxidative (soleus) muscle and 15-fold lower in cardiac muscle than in mixed skeletal muscle. The trace residual activity in ICR/IAn mice is present at the same level in soleus muscle, cardiac muscle and mixed skeletal muscle. Soleus muscles of ICR/IAn mice contain 1.5% of normal activity at pH 8.2 in the presence of Ca2+ and 30% of normal activity at pH 6.8 in the absence of Ca2+. Cardiac muscle contains 6% of normal activity at pH 8.2 in the presence of Ca2+ and 60% of normal activity at pH 6.8 in the absence of Ca2+. When isolated soleus muscles were incubated with adrenaline [epinephrine], the level of phosphorylase a in ICR/IAn mice rose from 2.8% in the absence of the hormone to 5.7% in the presence of the hormone. The level of phosphorylase a in normal mice varied from 2.4-11.1% in the absence of adrenaline and increased to 17.7-23.9% in the presence of the hormone. The trace phosphorylase kinase activity in ICR/IAn mice apparently is capable of phosphorylating phosphorylase b in vivo. This enzyme apparently is responsible for the very low level of phosphorylase a in resting soleus muscle or ICR/IAn mice and perhaps even in normal mice. Since the residual enzyme cannot be activated by cAMP-dependent protein kinase, the elevation of phosphorylase a by adrenaline may be caused by an inhibition of phosphorylase phosphatase. The possibility that this occurs through the activation of protein phosphatase inhibitor 1 by cAMP-dependent protein kinase is discussed. Incubation of soleus muscles with adrenaline decreased the activity ratio (.+-. glucose 6-phosphate) of glycogen synthase from 0.24-0.08 in ICR/IAn mice and 0.31-0.14 in C3H/He-mg or Swiss albino mice. The inactivation of glycogen synthase by adrenaline in resting soleus muscle apparently does not result from the activation of phosphorylase kinase by cAMP-dependent protein kinase. It is most likely mediated by a direct phosphorylation catalyzed by cAMP-dependent protein kinase, although the activation of protein phosphatase inhibitor 1 may contribute to the effect.


Accession: 006288172



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