Mediates responses to nitric oxide (NO) by catalyzing the biosynthesis of the signaling molecule cGMP. GTP = 3',5'-cyclic GMP + diphosphate Binds 1 or 2 heme groups per heterodimer. Heme is required for responding to nitric oxide, but not for catalytic activity. Activated by nitric oxide in the presence of magnesium or manganese ions. The active enzyme is formed by a heterodimer of an alpha and a beta subunit. Heterodimer with GUCY1A1 (PubMed:1352257, PubMed:23505436, PubMed:24669844). Can also form inactive homodimers in vitro (PubMed:23505436, PubMed:24669844). Detected in brain cortex and cerebellum (at protein level). There are two types of guanylate cyclases: soluble forms and membrane-associated receptor forms. Belongs to the adenylyl cyclase class-4/guanylyl cyclase family.