CPA (carboxypeptidase A) is a type of zinc-dependent metallopeptidase that participates in the hydrolysis of peptides. Major family members include CPA1, CPA2, and CPA3, which consist of multiple functional domains and are primarily located extracellularly or in the cytoplasm. CPA plays an important role in regulating protein degradation, activating or inactivating bioactive peptides, and modulating cell signaling. In different tissues and cells, the expression of CPA family members is specific, and mutations or dysregulation of their expression are associated with various diseases, including pancreatitis, tumors, and allergic diseases. The activity of CPA is regulated by pH, metal ions, and natural inhibitors, affecting its function in physiological and pathological processes.