The Cyclic guanosine monophosphate reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Cyclic guanosine monophosphate

\r\r\r \r\r\r Cyclic guanosine monophosphate (cGMP) is a cyclic nucleotide derived from guanosine triphosphate (GTP). cGMP acts as a second messenger much like cAMP, most notably by activating intracellular protein kinases in response to the binding of membrane-impermeable peptide hormones to the external cell surface.\r\r\r \r\r\r

Synthesis

\r\r\r \r\r\r cGMP synthesis is catalyzed by guanylate cyclase (GC) which converts GTP to cGMP. Membrane-bound GC is activated by peptide hormones such as the natriuretic factors, while nitric oxide typically stimulates cGMP synthesis in soluble GC.\r\r\r \r\r\r

Effects

\r\r\r \r\r\r cGMP is a common regulator of ion channel conductance, glycogenolysis, and cellular apoptosis. It also relaxes smooth muscle tissue.\r\r\r \r\r\r

Degradation

\r\r\r \r\r\r Cyclic nucleotide phosphodiesterases (PDE 1-6) degrade cGMP by hydrolyzing cGMP into 5'-GMP. (Sildenafil, the active ingredient in Viagra, inhibits PDE5 and increases the smooth muscle-relaxing effects of cGMP within the corpus cavernosum. Viagra can thus produce stronger erections in patients with erectile dysfunction by increasing bloodflow to the penis during sexual arousal.)\r\r\r \r\r\r

References

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• Cyclic nucleotide-dependent protein kinases: intracellular receptors for cAMP and cGMP action

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