Interaction of guanine phosphonomethoxyalkyl derivatives with GMP kinase isoenzymes.

Substrate activity and inhibitory potency of guanine phosphonomethoxyalkyl derivatives towards GMP kinase isoenzymes from L1210 cells were studied. 9-[2-(Phosphonomethoxy)ethyl]guanine (PMEG) and the (R)- and (S)-enantiomers of both 9-[3-hydroxy-2-(phosphonomethoxy)propyl]guanine (HPMPG) and 9-[2-(phosphonomethoxy)propyl]guanine (PMPG) were phosphorylated to the first step. Kinetic data showed that (R)-PMPG was a good substrate with a relative phosphorylation efficacy of 12% compared with the natural substrate GMP, whereas PMEG was a poor substrate with a relative phosphorylation efficacy of 1.1%. The structurally related 2,6-diaminopurine analogues 9-[2-(phosphonomethoxy)ethyl]-2, 6-diaminopurine (PMEDAP) and (R)- and (S)-9-[2-(phosphonomethoxy)propyl]-2,6-diaminopurine (PMPDAP) were not phosphorylated by any of the GMP kinase isoenzymes tested. The inhibitory activities of the individual compounds on GMP kinase isoenzymes decreased in the following order: (S)-HPMPG > (R)-PMPG > PMEG > (R)-HPMPG > (S)-PMPG > PMEDAP = (R)-PMPDAP = (S)-PMPDAP; each compound exerted a different type of inhibition.