Carboxypeptidase N2 (CPN2)

Carboxypeptidase N is a 280-kD tetrameric glycoprotein that is synthesized by the liver and secreted into the plasma. It consists of 2 identical 83-kD regulatory subunits and 2 identical 50-kD catalytic subunits (CPN1). Carboxypeptidase N has frequently been called serum or plasma carboxypeptidase B, which is misleading since the enzymatic and physical properties and the protein sequences of carboxypeptidase N and pancreatic carboxypeptidase B are quite distinct.By screening a liver expression library with antibodies against carboxypeptidase N, Tan et al. (1990) isolated a cDNA encoding the 83-kD regulatory subunit, or CPN2. The predicted 536-amino acid protein contains a region of twelve 24-residue leucine-rich repeats and 5 leucine zipper motifs.