Membrane guanylyl cyclase is an enzyme found in the membranes of certain cells. It plays a crucial role in converting guanosine triphosphate (GTP) into cyclic guanosine monophosphate (cGMP), a signaling molecule that helps regulate various physiological processes, including blood pressure and smooth muscle relaxation. This enzyme is activated by specific ligands, such as natriuretic peptides and nitric oxide. Once activated, membrane guanylyl cyclase increases cGMP levels, which then triggers a cascade of cellular responses. These responses can influence processes like vasodilation, neurotransmission, and cell growth.