Inhibition of nucleoside diphosphate kinase (NDPK/nm23) by cAMP analogues

Nucleoside diphosphate kinase (NDPK/nm23) ATP/GDP phosphotransferase activity and serine autophosphorylation is inhibited by N6-mbcAMP, 8-ClcAMP and 8-BrcAMP. Inhibition of the enzymatic activity largely depends on the concentration of ATP and becomes significant at ATP concentrations up to 0.5 mM and at effector concentrations measured in C6 cells stimulated with 1 mM cAMP analogue. N6-mbcAMP is a substrate of the enzyme. DbcAMP and 0'2-mbcAMP, cAMP analogues with a modified 0'2-ribose, did not affect the NDPK activity. Cyclic AMP is only a moderate inhibitor of NDPK even at low ATP concentrations. Possible inhibitory effects of cAMP and cAMP analogues on reported extra- and intracellular functions of NDPK/nm23 are discussed.