Carboxypeptidase Q (Cpq) is a member of the peptidase M28 family. PGCP is involved in a number of fundamental biological processes such as the hydrolysis of circulating peptides, catalyzing the hydrolysis of dipeptides with unsubstituted terminals into amino acids. Carboxypeptidase may play an important role in the liberation of thyroxine hormone from its thyroglobulin (Tg) precursor. The monomeric form is inactive while the homodimer is active.