Corin was first described as a trypsin-like serine proteinase in the heart which processed pro-atrial natriuretic peptide into the active form ANP. Corin cleaves pro-ANP at Arg98/Ser-99, and blocking Corin message inhibits pro-ANP processing. Null mutant mice lacking Corin develop hypertension, and a series of missense mutations have been identified in humans with high blood pressure and hypertension. Corin is a member of the type-II transmembrane serine proteinases, such as Hepsin, Epitheliasin, Matriptase and enteropeptidase. The Corin domain structure includes a cytoplasmic domain, a transmembrane domain, a spacer region, a frizzled-like domain, 5 LDL Receptor-like domains, another frizzled-like domain, 3 more LDLR-like repeats, a SRCR (Scavenger Receptor-Cysteine Rich) domain (also called macrophage scavenger-like domain), and finally the trypsin-like serine proteinase domain. The complex domain structure puts Corin into the “mosaic” TMPRSS family, so named because of the wide variety of domains.