Cyclic nucleotide-, Ca2- and nitric oxide-based signalling

The (reversible) phosphorylation of a protein substrate, X, typically results in a subtle change in the conformation of the phosphoprotein (denoted X-P) that is typically associated with a change in ligand binding and/or catalytic activity. Such phosphorylation is ultimately reversed through the operation of phosphoprotein phosphatases (PPs) that catalyse the hydrolytic dephosphorylation of phosphoproteins  

The cyclic nucleotides adenosine 3, 5 -cyclic monophosphate (cyclic AMP (cAMP)) and guanosine 3, 5 -cyc.lic monophosphate (cyclic GMP (c.GMP)) are second messengers generated by adenylyl (adenylate) cyclase (AC) and guanylyl (guanylate) cyclase (GC), respectively, in response to receptor occupation by particular primary messengers , that is, 

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Cyclic nucleotide-, Ca2+- and nitric oxide-based signalling... 

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