– 2′(3′)-O-Anthraniloyladenosine-5′-O-triphosphate (2′-ANT-ATP) and its isomer 3′-ANT-ATP are fluorescent derivatives of ATP that spontaneously isomerize. Emitting a maximum light of 428 nm when excited at 330 nm in water, 2′(3′)-ANT-ATP specifically inhibits several types of adenylyl cyclase (AC) including mammalian AC1, AC2, and AC5 with inhibition constants (Kis) of 130, 640, and 120 nM, respectively. It also inhibits Bordetella pertussis AC toxin CyaA with Kis of 1.3 µM (in the presence of manganese) and 20 µM (in the presence of magnesium), Bacillus anthracis AC toxin edema factor with Kis of 0.44 µM (with manganese) and 5.15 µM (with magnesium), and Escherichia coli recombinase A (RecA) with a Ki of 6.3 µM.