Carboxypeptidase A usually refers to the pancreatic exopeptidase

Exopeptidase

An exopeptidase is an enzyme produced in the pancreas that catalyses the removal of an amino acid from the end of a polypeptide chain. Exopeptidase cleaves the end of a polypeptide chain....

 which hydrolyzes peptide bonds of C-terminal residues with aromatic or aliphatic side chain

Side chain

In organic chemistry and biochemistry, a side chain is a chemical group that is attached to a core part of the molecule called "main chain" or backbone. The placeholder R is often used as a generic placeholder for alkyl group side chains in chemical structure diagrams. To indicate other non-carbon...

s. Most scientists in the field now refer to this enzyme as , and to a related pancreatic carboxypeptidase

Carboxypeptidase

A carboxypeptidase is a protease enzyme that hydrolyzes the peptide bond of an amino acid residue at the carboxy-terminal end...

 as .

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. (also known as mast-cell CPA) is involved in the digestion of proteins by mast cell

Mast cell

A mast cell is a resident cell of several types of tissues and contains many granules rich in histamine and heparin...

s. (previously known as CPA-3, but renumbered when mast-cell CPA was designated CPA-3) may be involved in tumor

Tumor

A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

 progression, but this enzyme has not been well studied. has not been well studied. 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

Zinc

Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 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

Divalent

In chemistry, a divalent ion or molecule has a valence of two and thus can form two bonds with other ions or molecules. An older term for divalent is bivalent....

 metals (cobalt

Cobalt

Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

, nickel

Nickel

Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

).

External links

• The MEROPS
  Merops
  Merops may refer to:* Merops , a genus of bee-eaters.* MEROPS, an on-line database for peptidases.It may also refer to several figures from Greek mythology:* King of Ethiopia, husband of Clymene, who lay with Helios and bore Phaethon...
  
  online database for peptidases and their inhibitors: M14.001