cGMP (or 3'-5'-cyclic
GMP[?]) is a
second messenger molecule, used for
intracellular signal transduction. It is made from
GTP[?] by
guanylate cyclase[?]. Its main purpose is the regulation of
protein kinases; it is also use to regulate the passage of
cations (for example,
Ca2+)through
ion channels, a mechanism used in
retina cells by
mammals.