Human Soluble Guanylate Cyclases (Adenylyl Cyclase 4/Guanylyl Cyclase Family) are heterodimeric (alpha/beta) nitric oxide-activated cytoplasmic enzymes that catalyze conversion of GTP to cGMP second messenger. The main receptors for nitric oxide in the cardiovascular system and for nitrovasodilator drugs, alpha/beta interaction is required for guanylyl cyclase activity. (NCI) [ ]