Glutamate carboxypeptidase

 

Glutamate carboxypeptidase (also known as carboxypeptidase G2, CPDG2, CPG2 or folate hydrolase G2) belongs to the peptidase M20A family.

G2 is a periplasmic enzyme that is synthesized with a signal peptide and is a dimeric zinc-dependent exopeptidase, with two domains, a catalytic domain, which provides the ligands for the two zinc ions in the active site, and a dimerization domain. It is known to cleave the C-terminal glutamate moiety from a wide range of N-acyl groups, including peptidyl, aminoacyl, benzoyl, benzyloxycarbonyl, folyl (shown in the reference reaction), and pteroyl groups to release benzoic acid, phenol, and aniline mustards. It is used clinically to treat methotrexate toxicity by hydrolysing methotrexate to inactive and non-toxic metabolites. It is also proposed for use in antibody-directed enzyme prodrug therapy against tumor cells.

 

Reference Protein and Structure

Sequence
P06621 UniProt (3.4.17.11) IPR017150 (Sequence Homologues) (PDB Homologues)
Biological species
Pseudomonas sp. RS-16 (Bacteria) Uniprot
PDB
1cg2 - CARBOXYPEPTIDASE G2 (2.5 Å) PDBe PDBsum 1cg2
Catalytic CATH Domains
3.40.630.10 CATHdb (see all for 1cg2)
Cofactors
Zinc(2+) (2)
Click To Show Structure

Enzyme Reaction (EC:3.4.17.11)

water
CHEBI:15377ChEBI
+
folate(2-)
CHEBI:62501ChEBI
→
glutamate(2-)
CHEBI:29987ChEBI
+
4-{[(2-amino-4-oxo-3,4-dihydropteridin-6-yl)methyl]amino}benzoic acid
CHEBI:37055ChEBI
Alternative enzyme names: N-pteroyl-L-glutamate hydrolase, Carboxypeptidase G, Carboxypeptidase G1, Carboxypeptidase G2, Glutamyl carboxypeptidase,

Enzyme Mechanism

Introduction

The catalytic water bridges the two divalent zinc cations and is activated by this interaction and with Glu175. Glu175 is thought to deprotonate the water, which attacks the substrate. The intermediate formed then collapses, with deprotonation of Glu175 to produce the products.

Catalytic Residues Roles

UniProt PDB* (1cg2)
Glu175 Glu175(153)A Acts as a general acid/base. proton shuttle (general acid/base)
His112, Asp141, Glu200 His112(90)A, Asp141(119)A, Glu200(178)A Forms part of the zinc 2 binding site. metal ligand
Asp141, Glu176, His385 Asp141(119)A, Glu176(154)A, His385(363)A Forms part of the zinc 1 binding site. metal ligand
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

References

  1. Rowsell S et al. (1997), Structure, 5, 337-347. Crystal structure of carboxypeptidase G2, a bacterial enzyme with applications in cancer therapy. DOI:10.1016/s0969-2126(97)00191-3. PMID:9083113.
  2. Turra KM et al. (2012), J Mol Model, 18, 1867-1875. Molecular modeling approach to predict a binding mode for the complex methotrexate-carboxypeptidase G2. DOI:doi:10.1007/s00894-011-1196-z.

Step 1.

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Catalytic Residues Roles

Residue Roles
Glu175(153)A proton shuttle (general acid/base)
His112(90)A metal ligand
Asp141(119)A metal ligand
Glu176(154)A metal ligand
Glu200(178)A metal ligand
His385(363)A metal ligand

Chemical Components

Step 1.

Contributors

Gemma L. Holliday, Nozomi Nagano, Craig Porter