Metallocarboxypeptidases

Abstract

Metallocarboxypeptidases (CP) catalyze the removal of C‐terminal amino acids from proteins and/or peptides. The different members of the CP family differ in their specificity for C‐terminal residues and physiological function and can be divided into two subfamilies. Members of the A/B subfamily are generally produced as proenzymes, contain an approximately 300‐residue CP catalytic domain, have greatest amino acid sequence identity to the exocrine pancreatic enzymes CPA and CPB, and prefer hydrophobic or basic residues. They function in the breakdown of peptides in food or in other physiological processes ranging from inflammation to fibrinolysis. Members of the N/E group cleave C‐terminal basic residues and are not produced as inactive proenzymes but contain an approximately 80‐residue region following the 300‐residue CP domain with structural homology to transthyretin. They act either extra‐ or intracellularly in the processing of peptide hormones and neurotransmitters and other physiologically relevant peptides. The tertiary folding of CPs corresponds to the α/β hydrolase fold and is formed by a central mixed parallel/antiparallel eight‐strand β‐sheet, with a 120° twist between the first and the last strand, over which eight α‐helices pack on both sides to form a globular molecule. All of the enzymatically active CPs bind one atom of Zn 2+ at the active site. Some members of the CP family that are inactive against standard CP substrates lack some of the cation‐binding ligands and may therefore not be able to bind the metal.

The Three-Dimensional Structures of Tick Carboxypeptidase Inhibitor in Complex with A/B Carboxypeptidases Reveal a Novel Double-headed Binding Mode

“…19,32 The C-terminal tail also constitutes the primary binding site of PCI and LCI, docking into the active site of the enzyme and leading to a stopper-like inhibition. 2,12 The C-terminal residue of PCI and LCI (Gly39 and Glu66) also is cleaved off by the carboxypeptidase but, unlike in TCI-CP complexes, this last residue remains bound in the S1 0 subsite of the enzyme's active site. 8,10 The number of interactions between this cleaved-off residue and the active site of the carboxypeptidase might determine its presence (PCI, LCI) or absence (TCI) after the crystallization process.…”

“…8,10 Both proteins inhibit carboxypeptidases via a substrate-like interaction of their C-terminal tail with the active-site groove of the enzyme. 11,12 Numerous protease inhibitors have been described in hematophagous organisms, most notably those directed toward their host's blood coagulation factors such as thrombin and factor Xa. 13,14 The structures of several of these inhibitors in complex with different target proteases have been solved by X-ray crystallography.…”

Tri-domain Bifunctional Inhibitor of Metallocarboxypeptidases A and Serine Proteases Isolated from Marine Annelid Sabellastarte magnifica

“…Besides a role in digestive protein degradation, these enzymes are also key elements of selective proteolysis-regulated physiological processes such as blood coagulation/fibrinolysis, inflammation, prohormone and neuropeptide processing, local anaphylaxis, and insect/plantattack/defense strategies, among others (1,2). The biological actions of many proteases are controlled by their interaction with specific proteinaceous inhibitors.…”

Comparative study on activation mechanism of carboxypeptidase A1, A2 and B: First insights from steered molecular dynamics simulations

“…Pancreatic and pancreatic-like carboxypeptidases (CPs) are a family of zinc-containing exopeptidases, involved in the digestion process, which catalyze hydrolysis of C-terminal amino acids from their substrates [1][2][3]. They are naturally secreted as inactive precursors or zymogens (known as procarboxypeptidases, PCPs) and are subsequently activated by proteolytic cleavage of trypsin-like protease, resulting in the release of prosegment and full activation [4].…”