Carboxypeptidase M (CPM) belongs to the peptidase M14 family. CPM specifically removes C-terminal basic residues (Arg or Lys) from peptides and proteins, and the activity is inhibited by O-phenanthroline and MGTA and activated by cobalt. The amino acid sequence of CPM indicated that the C-terminal hydrophobic region might be a signal for membrane attachment via a glycosylphosphatidylinositol (GPI) anchor. CPM is involved in peptide metabolism on both the cell surface and in extracellular fluids. CPM functions not only as a protease but also as a binding partner in cell-surface protein-protein interactions.