Stimulation of the cyclic AMP-dependent protein kinase-catalyzed phosphorylation of phosphorylase kinase by micromolar concentrations of spermine

The phosphorylation of phosphorylase kinase by cyclic AMP-dependent protein kinase (A-kinase) is stimulated approximately 2-fold by spermine and spermidine. Half maximal effects were observed at 10 microM and 150 microM of spermine and spermidine, respectively. The phosphorylations of other substrates of A-kinase such as glycogen synthase, histone, and casein are not stimulated by these two polyamines. The rates, but not the final extents, of phosphorylation of both the alpha and beta subunits of phosphorylase kinase by A-kinase are stimulated by spermine. The results indicate that spermine and spermidine may play an important role in the activation of glycogenolysis in skeletal muscle.