Particulate guanylyl cyclases: multiple mechanisms of activation

Cyclic GMP (cGMP), a key messenger in several signal transduction pathways, is synthesized from GTP by a family of enzymes termed guanylyl cyclases, w hich are found in two forms: cytosolic (soluble) and membrane-bound (partic ulate). The past decade has brought significant progress in understanding t he molecular mechanisms that underlie the regulation of particulate guanyly l cyclases and new members of their family have been identified. It has bec ome more evident that the basic mechanism of catalysis of guanylyl cyclases is analogous to that recognized in adenylyl cyclases. Here we review the k nown basic mechanisms that contribute to the regulation of particulate guan ylyl cyclases.