Effects of polyamines on nucleosidediphosphate kinase activity.

Effects of naturally occurring polyamines were tested on the activity of bovine liver nucleosidediphosphate kinase with ATP as phosphoryl donor and eight nucleosidediphosphates as phosphoryl acceptors. The enzyme was either stimulated, inhibited, or unaffected depending upon the nucleosidediphosphate substrate and the polyamine, indicating that a general cation effect is not a sole mechanism of polyamine action. This selectivity and specificity of the effects with respect to both the polyamines and the nucleosidediphosphates leads us to speculate that an action of polyamines on nucleosidediphosphate kinase may play a significant role in the regulation of specific nucleosidetriphosphate synthesis $\text{in vivo}$.