In 1956 Edwin Krebs and Edmond Fischer discovered that adenosine triphosphate (ATP) is required for the conversion of glycogen phosphorylase b to glycogen phosphorylase a.
Evgeny Fesenko, Stanislav Kolesnikov, and Arkady Lyubarsky discovered in 1985 that cyclic guanosine monophosphate (cGMP) can initiate the photoresponse in rods.