Guanylyl cyclases are enzymes that convert GTP (guanosine triphosphate) into cGMP (cyclic guanosine monophosphate), a crucial signaling molecule in various biological processes. They play a significant role in regulating blood pressure, smooth muscle relaxation, and neurotransmission. There are two main types of guanylyl cyclases: soluble guanylyl cyclases, which are activated by nitric oxide, and membrane guanylyl cyclases, which are activated by specific ligands like natriuretic peptides. The production of cGMP leads to various physiological effects, including vasodilation and inhibition of platelet aggregation.