CPA3

Carboxypeptidase A3 (mast cell carboxypeptidase A), also known as CPA3, is an enzyme which in humans is encoded by the CPA3 is_associated_with::gene.

Function
Altogether, there are 22-23 members of the metallocarboxypeptidase gene family in most mammals. CPA3 is one of 8-9 members of the A/B subfamily that includes the well-studied pancreatic enzymes carboxypeptidase A1 (CPA1), carboxypeptidase A2 (CPA2), and is_associated_with::carboxypeptidase B. This subfamily includes 6 carboxypeptidase A-like enzymes, numbered 1-6. The enzyme now called CPA3 was originally named mast cell carboxypeptidase A, and another protein was initially called CPA3 (Huang et al., 1999). A gene nomenclature committee renamed mast cell carboxypeptidase A as CPA3, and the original CPA3 reported by Huang et al. became CPA4 to reflect the order of their discovery.

CPA3 is secreted from mast cells and has a pH optimum in the neutral to basic range. It resembles pancreatic carboxypeptidases A1 in cleaving COOH-terminal aromatic and aliphatic amino acid residues. CPA3 functions together with is_associated_with::endopeptidases secreted from is_associated_with::mast cells such as is_associated_with::chymases and is_associated_with::tryptases to degrade proteins and peptides. Upon mast cell activation and is_associated_with::degranulation, CPA3, the chymases, and tryptases are released in complexes with heparin proteoglycan.