Decoyinine is a selective inhibitor of GMP synthetase (GMPS). IC50 & Target: GMPS^[1]. In Vitro: Decoyinine is an analog of adenosine which causes a decrease in intracellular GTP levels by inhibition of GMP synthetase. Decoyinine exerts a stimulatory effect on oaamylase synthesis only in the strain in which the catabolite repression component of a-amylase regulation has been rendered inoperable by the gra-10 mutation. The apparent stimnulation of a-amylase activity in WLN-11 by Decoyinine is not an artifactual effect exerted at the level of enzyme activity itself. It is observed that purine nucleotides, most notably GMP, exhibits a dramatic inhibitory effect on the activity of Bacillus circulans F-2 amylase and a less-pronounced inhibitory effect on B. subtilis aamylase. At the concentration used in the experiments (1.07 mM), Decoyinine has no effect in vitro on B. subtilis WLN-11 oaamylase activity. At the same concentration, GMP exerts a slight inhibitory effect on aamylase activity^[2]. In Vivo: It is showed that Decoyinine (Angustmycin A) treatment hinders tumor growth in xenograft mouse model. Moreover, like GMPS activity, the effect of Decoyinine does not appear to be subtype specific as it impairs growth of xenografts from cells harboring NRASQ61R (SK-Mel-103) or BRAFV600E (SK-Mel-28) mutations^[1].