Serine-type endopeptidase involved in atrial natriuretic peptide (NPPA) and brain natriuretic peptide (NPPB) processing (PubMed:10880574, PubMed:20489134, PubMed:21288900, PubMed:21763278). Converts through proteolytic cleavage the non-functional propeptides NPPA and NPPB into their active hormones, ANP and BNP(1-32) respectively, thereby regulating blood pressure in the heart and promoting natriuresis, diuresis and vasodilation (PubMed:10880574, PubMed:20489134, PubMed:21288900, PubMed:21763278). Proteolytic cleavage of pro-NPPA also plays a role in female pregnancy by promoting trophoblast invasion and spiral artery remodeling in uterus (PubMed:22437503). Also acts as a regulator of sodium reabsorption in kidney (By similarity). {ECO:0000250|UniProtKB:Q9Z319, ECO:0000269|PubMed:10880574, ECO:0000269|PubMed:20489134, ECO:0000269|PubMed:21288900, ECO:0000269|PubMed:21763278, ECO:0000269|PubMed:22437503}. [Isoform 2]: Has weaker endopeptidase activity compared to isoform 1. This is the function of CORIN (corin, serine peptidase, ENSG00000145244).