Nuclear magnetic resonance studies on the mechanism of regulation of glycogenolysis in contracting skeletal muscle.
In vitro biochemical experiments showed that glycogenolysis can be regulated by two different mechanisms; i.e., Ca regulation at the phosphorylase step and phosphate-product regulation at the phosphofructokinase step. Recent studies on glycogenolysis in living vertebrate skeletal muscles by use of 31P nuclear magnetic resonance (NMR) presented evidence that glycogenolysis in vivo is regulated by Ca released from the sarcoplasmic reticulum. The present 31P NMR studies on living frog skeletal muscle indicated that glycogenolysis is further regulated by the phosphate products accumulated as the result of contractile activities. Therefore it was concluded that the glycogenolysis in vivo is actually regulated by the two mechanisms as predicted by in vitro biochemical studies.