Principles of Biochemistry

9.2.3.2 cGMP as second messenger

Hormones such as insulin and growth hormone affect the guanylate cyclase cGMP system.

This will increase the intracellular concentration of cGMP dependent protein kinases.

The active cGMP protein kinase would in turn bring about phosphorylation of specific cellular proteins to change their activities, leading to relaxation of, smooth muscles, vasodilation and other effects. cGMP acts as a second messenger to activate guanylate cyclase and thereby increasing the concentration of cGMP inside the cell.

The atriopeptins, a family of peptides, produced in cardiac atrial, tissues cause natriuresis, dieuresis, vasodilatation and inhibition of the testosterone secretion.

These peptides (eg. atrial natriuretic facture) bind to and activate the membrane bound form guanylate cyclase. This results in an increase of cGMP .