Cyclic guanosine monophosphate (cGMP) is a nucleotide that plays a crucial role in cellular signaling. It is synthesized from guanosine triphosphate (GTP) by the enzyme guanylate cyclase. cGMP acts as a second messenger, transmitting signals from various hormones and neurotransmitters to target cells, influencing processes such as smooth muscle relaxation and blood vessel dilation. In addition to its role in vasodilation, cGMP is involved in regulating various physiological functions, including vision and neurotransmission. The breakdown of cGMP is facilitated by the enzyme phosphodiesterase, which helps maintain appropriate levels of this important signaling molecule within cells.