Carboxypeptidase A3 (CPA3)

The enzyme now called CPA3 was originally named mast cell carboxypeptidase A, and another protein was initially called CPA3. 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 endopeptidases secreted from mast cells such as chymases and tryptases to degrade proteins and peptides. Upon mast cell activation and degranulation, CPA3, the chymases, and tryptases are released in complexes with heparin proteoglycan.