– 2′(3′)-O-Anthraniloylguanosine-5′-O-triphosphate (2′-ANT-GTP) and 3′-ANT-GTP are fluorescent derivatives of GTP that exhibit spontaneous isomerization. 2′(3′)-ANT-GTP features an emission peak at 428 nm when excited at 330 nm in aqueous conditions. It functions as an inhibitor of several adenylyl cyclases, notably mammalian adenylyl cyclase 1 (AC1; Ki = 10 nM with manganese), inhibits B. anthracis adenylyl cyclase toxin edema factor (Kis = 4.1 and 13 µM with manganese and magnesium, respectively), and B. pertussis adenylyl cyclase toxin CyaA (Ki = 29 µM with manganese).