Calcium--calmodulin-dependent activation of porcine liver phosphorylase kinase.

Porcine liver phosphorylase kinase was activated about 1.5-fold by calmodulin in a calcium-dependent manner. Half-maximal stimulation was observed at about 80 nM calmodulin and the activation was almost pH-independent. The specific binding of porcine liver phosphorylase kinase to calmodulin--Sepharose affinity column exhibited an absolute dependence upon the presence of calcium. The physiological role of the calmodulin-dependent activation for liver phosphorylase kinase is discussed.