Carboxypeptidase A

Carboxypeptidase A, from bovine pancreas

Carboxypeptidase A usually refers to the pancreatic exopeptidase which hydrolyzes peptide bonds of C-terminal residues with aromatic or aliphatic side chains. Most scientists in the field now refer to this enzyme as CPA1, and to a related pancreatic carboxypeptidase as CPA2.

In addition, there are 4 other mammalian enzymes named CPA-3 through CPA-6, and none of these are expressed in the pancreas. Instead, these other CPA-like enzymes have diverse functions.

• CPA3 (also known as mast-cell CPA) is involved in the digestion of proteins by mast cells.
• CPA4 (previously known as CPA-3, but renumbered when mast-cell CPA was designated CPA-3) may be involved in tumor progression, but this enzyme has not been well studied.
• CPA5 has not been well studied.
• CPA6 is expressed in many tissues during mouse development, and in adult shows a more limited distribution in brain and several other tissues. CPA6 is present in the extracellular matrix where it is enzymatically active. A human mutation of CPA-6 has been linked to Duane's syndrome (abnormal eye movement). Recently, mutations in CPA6 were found to be linked to epilepsy.

CPA-1 and CPA-2 (and presumably all other CPAs) contain a zinc atom at the active site. Loss of the zinc leads to loss of activity, which can be replaced easily by zinc, and also by some other divalent metals (cobalt, nickel).

See also

• Carboxypeptidase A inhibitor
• Carboxypeptidase
• Carboxypeptidase E

External links

• The MEROPS online database for peptidases and their inhibitors: M14.001
• MeSH Carboxypeptidases+A