Sandbox Reserved 1054: Difference between revisions

<scene name='69/694222/3cpaoverview/1'>Carboxypeptidase A (peptidyl-L-amino acid hydrolase, EC 3.4.17.1, often abbreviated CPA)</scene> is a metalloexopeptidase that hydrolytically cleaves peptides at the [http://en.wikipedia.org/wiki/C-terminus C-terminal] peptide bond containing hydrophobic side chains <ref name="CPA1">Bukrinsky JT, Bjerrum MJ, Kadziola A. 1998. Native carboxypeptidase A in a new crystal environment reveals a different conformation of the important tyrosine 248. ''Biochemistry''. 37(47):16555-16564. [http://pubs.acs.org/doi/abs/10.1021/bi981678i DOI: 10.1021/bi981678i]</ref>  Specifically, CPA is a Zn²⁺ [http://en.wikipedia.org/wiki/Metalloprotein#Metalloenzymes metalloenzyme] that carries out the hydrolysis of C-terminal polypeptide residues through the [http://en.wikipedia.org/wiki/Deprotonation deprotonation] of a water molecule that is coordinated to the Zn²⁺ ion in the enzyme's [http://en.wikipedia.org/wiki/Active_site active site].<ref name="CPA2">Christianson DW, Lipscomb WN. 1989. Carboxypeptidase A. ''Acc. Chem. Res.'' 22:62-69.</ref>  From bovine pancreas, CPA has been crystallized in a new environment alongside two Zn²⁺ ions, one catalytic, the other inhibitory. The inhibitory Zn²⁺ ion in this more recent crystal structure not only prevents 1CPX from undergoing its hydrolysis mechanism (BLUE LINK), but also this crystallographic data reveals a different conformation of the Tyr248 (GREEN LINK) residue suggesting alternative mechanistic behavior (CITE). 1CPX consists of a single polypeptide chain that contains 307 amino acids.  Produced in bovine pancreas, CPA itself must first be activated by either [http://en.wikipedia.org/wiki/Trypsin trypsin] or [http://en.wikipedia.org/wiki/Chymotrypsin chymotrypsin] in order to achieve an active form that serves its biological function.<ref name="CPA1" />. This crystallographic data presents 1CPX activated by trypsin in its β-form and orthorhombic crystal form.