Synthesizes cyclic GMP (cGMP) from GTP. May play a role in embryogenesis. GTP = 3',5'-cyclic GMP + diphosphate Binds 1 or 2 heme groups per heterodimer. May be regulated by molecular oxygen. Probably not activated by nitric oxide (NO) (By similarity). Heterodimer; with other soluble guanylate cyclases. Expressed in a pair of bilaterally symmetric neurons in the head. There are two types of guanylate cyclases: soluble forms and membrane-associated receptor forms. Belongs to the adenylyl cyclase class-4/guanylyl cyclase family.