Carboxypeptidase N (arginine carboxypeptidase or CPN) cleaves basic amino acid residues from the carboxy terminal of peptides and proteins. The enzyme plays a central role in regulating the biologic activity of peptides such as kinins and anaphylatoxins, and therefore is also known as kininase-1 and anaphylatoxin inactivator. CPN is a tetrameric complex consisting of two identical regulatory subunits (CPN reg) and two identical catalytic subunits (CPN cat). The two glycosylated CPN reg subunits protect the two CPN cat subunits and keep them in the circulation. CPN reg is a member of the leucinerich repeat family of proteins and the gene which encodes CPN reg maps to human chromosome 8p22-p23. CPN cat is a member of the regulatory B-type carboxypeptidase group and the gene which encodes CPN cat maps to human chromosome 10.