Cardiac hormone that plays a key role in mediating cardio-renal homeostasis (PubMed:8182124). May also function as a paracrine antifibrotic factor in the heart (PubMed:10737768). Acts by specifically binding and stimulating NPR1 to produce cGMP, which in turn activates effector proteins that drive various biological responses (PubMed:8182124). Likely involved in regulating the extracellular fluid volume and maintaining the fluid-electrolyte balance through natriuresis, diuresis, kaluresis and chloruresis (By similarity). Detected in blood. Expressed abundantly in the ventricle, and in a lesser extent in the atrium (at protein level). The precursor molecule is proteolytically cleaved by the endoprotease Furin to produce brain natriuretic peptide 45 (By similarity). May undergo further proteolytic cleavage by various proteases such as DPP4, MME and possibly FAP, to give rise to a variety of shorter peptides (By similarity). May be cleaved at Ser-91 by the prolyl endopeptidase FAP (seprase) activity (in vitro) (By similarity). May be degraded by IDE (By similarity). During IDE degradation, the resulting products initially increase the activation of NPR1 and can also stimulate NPR2 to produce cGMP before the fragments are completely degraded and inactivated by IDE (in vitro) (By similarity). Mice are viable and fertile and do not display gross skeletal abnormalities. Fluid-electrolyte balance and blood pressure remain normal although an increased rate of focal fibrotic lesions is observed within the cardiac ventricles. Belongs to the natriuretic peptide family.