. . . . . . . . . . . . . . . . . . . "A guanine nucleotide containing one phosphate group which is esterified to the sugar moiety in both the 3'- and 5'-positions. It is a cellular regulatory agent and has been described as a second messenger. Its levels increase in response to a variety of hormones, including acetylcholine, insulin, and oxytocin and it has been found to activate specific protein kinases. (From Merck Index, 11th ed)"@en . . . . . . . . . "experimental"@en . . "7665-99-8"@en . "Guanosine-3',5'-monophosphate"@en . . "Cyclic Guanosine Monophosphate"@en . . . . . . .