Activation of phosphorylase kinase from brain by small amounts of calcium ion

E lectrical stimulation of brain results in an enhancement of glycogen breakdown (K ing , L owry , P assonneau and V enson , 1967) and one should therefore expect exitation to be linked in some way to glycogen metabolism. Stimulation of muscle cells, which induces contraction, also increases glycogen breakdown. In this case it has been shown that a minute amount of Ca 2+ , which couples excitation and contraction, also serves as a link between excitation and glycogenolysis (O zawa , H osoi and E bashi , 1967). A small amount of Ca 2+ , released into the sarcoplasm as a result of excitation of the cell membrane, activates phosphorylase kinase. The activated kinase, in turn, converts phosphorylase α (the inactive form of phosphorylase) to phosphorylasea (the active form). The present communication summarizes the evidence that a similar mechanism operates in brain.