2026-04-17T06:08:32Zhttps://recercat.cat/oai/request

oai:recercat.cat:2072/4394812026-03-13T05:51:49Zcom_2072_98col_2072_378192

00925njm 22002777a 4500 dc García Guerrero, María del Carmen author Garcia-Pardo, Javier author Berenguer De La Cuesta, Esther author Fernandez-Alvarez, Roberto author Barfi, Gifty B. author Lyons, Peter J. author Avilés, Francesc Xavier author Huber, Robert author Lorenzo Rivera, Julia author Reverter Cendrós, David author 2018 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 Nerita versicolor. 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. Carboxypeptidase Protein digestion Crystal structure Acidic protease Crystal structure and mechanism of human carboxypeptidase O : insights into its specific activity for acidic residues