Biochem/physiol Actions An important second messenger, cGMP is a major intracellular mediator of extracellular signals such as nitric oxide and natriuretic peptides. Cyclic GMP interacts with three types of intracellular receptor proteins: cGMP-dependent protein kinases, cGMP-regulated channels, and cGMP-regulated cyclic nucleotide phosphodiesterases. A primary action of elevated cGMP levels in vivo is the stimulation of cGMP-dependent protein kinase (PKG). Other Notes Tandem Mass Spectrometry data independently generated by Scripps Center for Metabolomics is available to view or download in PDF. G7504.pdf Tested metabolites are featured on Scripps Center for Metabolomics METLIN Metabolite Database. To learn more, visit sigma.com/metlin.