Carboxypeptidase A: Difference between revisions

'''Carboxypeptidase A (peptidyl-L-amino acid hydrolase, EC 3.4.17.1, often abbreviated CPA)''' is a metalloexopeptidase whose biological function is to cleave the C-terminal amino acid residues from polypeptide substrates.  Specifically, CPA is one member of a large group of Zn²⁺ metalloenzymes that carries out the hydrolysis of C-terminal polypeptide residues through the deprotonation of a water molecule that is coordinated to the Zn²⁺ ion in the enzyme's active site.  CPA consists of a single polypeptide chain that contains 307 amino acids.  Produced in the pancreas, CPA itself must first be modified by trypsin and chymotrypsin in order to achieve an active form that serves its biological function.  Although different biologically active forms of CPA are found across different species, including humans, much research has investigated bovine pancreatic zinc carboxypeptidase A.  X-ray crystallography has demonstrated that bovine CPA has the ability to bind two Zn²⁺ ions in its active site, in which the binding of one Zn²⁺ is catalytic, while the binding of a second Zn²⁺ inhibits the hydrolysis reaction mechanism.