5MRV

Crystal structure of human carboxypeptidase O in complex with NvCI

Summary for 5MRV

• Entry DOI: 10.2210/pdb5mrv/pdb
• Descriptor: Carboxypeptidase O, Metallocarboxypeptidase inhibitor, ZINC ION, ... (5 entities in total)
• Functional Keywords: digestive metallocarboxypeptidase, food digestion, carboxypeptidase inhibitor, brush border enzyme, hydrolase
• Biological source: Homo sapiens (Human); More
• Cellular location: Apical cell membrane ; Lipid-anchor, GPI-anchor : Q8IVL8
• Total number of polymer chains: 3
• Total formula weight: 89009.27

Authors

Garcia-Pardo, J.,Garcia-Guerrero, M.C.,Fernandez-Alvarez, R.,Lyons, P.,Aviles, F.X.,Lorenzo, J.,Reverter, D. (deposition date: 2016-12-27, release date: 2018-01-17, Last modification date: 2024-10-23)

Primary citation

Garcia-Guerrero, M.C.,Garcia-Pardo, J.,Berenguer, E.,Fernandez-Alvarez, R.,Barfi, G.B.,Lyons, P.J.,Aviles, F.X.,Huber, R.,Lorenzo, J.,Reverter, D.
Crystal structure and mechanism of human carboxypeptidase O: Insights into its specific activity for acidic residues.
Proc. Natl. Acad. Sci. U.S.A., 115:E3932-E3939, 2018

PubMed Abstract: Human metallocarboxypeptidase O (hCPO) is a recently discovered digestive enzyme localized to the apical membrane of intestinal epithelial cells. Unlike pancreatic metallocarboxypeptidases, hCPO is glycosylated and produced as an active enzyme with distinctive substrate specificity toward C-terminal (C-t) acidic residues. Here we present the crystal structure of hCPO at 1.85-Å resolution, both alone and in complex with a carboxypeptidase inhibitor (NvCI) from the marine snail The structure provides detailed information regarding determinants of enzyme specificity, in particular Arg275, placed at the bottom of the substrate-binding pocket. This residue, located at "canonical" position 255, where it is Ile in human pancreatic carboxypeptidases A1 (hCPA1) and A2 (hCPA2) and Asp in B (hCPB), plays a dominant role in determining the preference of hCPO for acidic C-t residues. Site-directed mutagenesis to Asp and Ala changes the specificity to C-t basic and hydrophobic residues, respectively. The single-site mutants thus faithfully mimic the enzymatic properties of CPB and CPA, respectively. hCPO also shows a preference for Glu over Asp, probably as a consequence of a tighter fitting of the Glu side chain in its S1' substrate-binding pocket. This unique preference of hCPO, together with hCPA1, hCPA2, and hCPB, completes the array of C-t cleavages enabling the digestion of the dietary proteins within the intestine. Finally, in addition to activity toward small synthetic substrates and peptides, hCPO can also trim C-t extensions of proteins, such as epidermal growth factor, suggesting a role in the maturation and degradation of growth factors and bioactive peptides.

PubMed: 29636417
DOI: 10.1073/pnas.1803685115

Experimental method

X-RAY DIFFRACTION (1.854 Å)