Carboxypeptidase O (CPO)

Carboxypeptidase O is a membrane-anchored brush-border enzyme expressed predominantly in intestinal epithelial cells, where it complements the activity of other digestive carboxypeptidases (such as CPA and CPB) by removing C-terminal acidic amino acids from dietary proteins and peptides. Unlike other pancreatic carboxypeptidases, CPO is produced in an active form, does not require an N-terminal prodomain for folding, and is glycosylated for enhanced proteolytic stability. Its high specificity for acidic residues is determined by Arg275 in the substrate binding pocket, and the enzyme exhibits a preference for glutamate over aspartate. CPO is also found associated with lipid droplets in the early secretory pathway and may play roles in lipid homeostasis. Despite broad conservation among vertebrates, no diseases are currently linked to CPO dysfunction, and no therapeutics directly target this enzyme in clinical settings. CPO is primarily relevant for digestive physiology and basic research, and not currently a clinical therapeutic target. It is sufficiently well-characterized in terms of sequence, structure, and function.

Other names

Metallocarboxypeptidase OMetallocarboxypeptidase CCarboxypeptidase OCPO

Cleavage of C-terminal acidic and polar amino acids from substrate proteins and peptides. Requires the presence of a zinc ion in its active site for catalytic activity; glycosylphosphatidylinositol (GPI) anchor targets CPO to the apical membrane of intestinal epithelial cells.