guanyl-5'-yl imidodiphosphate ( gpp ( nh ) p ) , a nucleotide phosphohydrolase-resistant analog of gtp , caused inhibitory and stimulatory effects on the basal adenylate cyclase activity of rat synaptosomal fractions when manganese was present in the assay mixture , whereas the nucleotide caused only a stimulatory effect when magnesium was employed .
C0018366
gpp ( nh ) p
C0018353
gtp