Acetylglutamate kinase

 

Catalyses the ATP-dependent phosphorylation of N-acetyl-L-glutamate (NAG). NAG fulfils distinct biological roles in lower and higher organisms. In prokaryotes, lower eukaryotes and plants it is the first intermediate in the biosynthesis of arginine, whereas in ureotelic (excreting nitrogen mostly in the form of urea) vertebrates, it is an essential allosteric cofactor for carbamoyl phosphate synthetase I (CPSI), the first enzyme of the urea cycle. This enzyme is present only in microorganisms and plants but absent in mammals, and as a result it is an attractive target for antimicrobial or biocidal development.

 

Reference Protein and Structure

Sequence
Q9SCL7 UniProt (2.7.2.8) IPR004662 (Sequence Homologues) (PDB Homologues)
Biological species
Arabidopsis thaliana (Thale cress) Uniprot
PDB
4usj - N-acetylglutamate kinase from Arabidopsis thaliana in complex with PII from Chlamydomonas reinhardtii (2.85 Å) PDBe PDBsum 4usj
Catalytic CATH Domains
3.40.1160.10 CATHdb (see all for 4usj)
Cofactors
Magnesium(2+) (1)
Click To Show Structure

Enzyme Reaction (EC:2.7.2.8)

N-acetyl-L-glutamate(2-)
CHEBI:44337ChEBI
+
ATP(4-)
CHEBI:30616ChEBI
→
N-acetyl-L-gamma-glutamyl phosphate(3-)
CHEBI:57936ChEBI
+
ADP(3-)
CHEBI:456216ChEBI
Alternative enzyme names: N-acetylglutamate 5-phosphotransferase, N-acetylglutamate kinase, N-acetylglutamate phosphokinase, N-acetylglutamic 5-phosphotransferase, Acetylglutamate phosphokinase,

Enzyme Mechanism

Introduction

Three successive steps have been proposed during phosphoryl transfer based on crystal structure: at the beginning, when the attacking and leaving O atoms and the P atom are imperfectly aligned and the distance between the attacking O atom and the P atom is 2.8A; midway, at the bipyramidal intermediate, with nearly perfect alignment and a distance of 2.3A; and, when the transfer is completed. The transfer occurs in line and is strongly associative, with Lys8 and Lys217 stabilising the transition state and the leaving group, respectively.

Catalytic Residues Roles

UniProt PDB* (4usj)
Asp162 Asp162A D162 organises and activates the catalytic groups. activator, steric role
Lys8, Gly11 (main-N), Gly45 (main-N), Lys217 Lys8A, Gly11A (main-N), Gly45A (main-N), Lys217A Acts as a transition state stabiliser. transition state stabiliser
*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. Gil-Ortiz F et al. (2003), J Mol Biol, 331, 231-244. The Course of Phosphorus in the Reaction of N-Acetyl-l-glutamate Kinase, Determined from the Structures of Crystalline Complexes, Including a Complex with an AlF4− Transition State Mimic. DOI:10.1016/s0022-2836(03)00716-2. PMID:12875848.
  2. Gil-Ortiz F et al. (2010), J Mol Biol, 399, 476-490. Two crystal structures of Escherichia coli N-acetyl-L-glutamate kinase demonstrate the cycling between open and closed conformations. DOI:10.1016/j.jmb.2010.04.025. PMID:20403363.
  3. Marco-Marín C et al. (2003), J Mol Biol, 334, 459-476. Site-directed mutagenesis of Escherichia coli acetylglutamate kinase and aspartokinase III probes the catalytic and substrate-binding mechanisms of these amino acid kinase family enzymes and allows three-dimensional modelling of aspartokinase. PMID:14623187.

Step 1.

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Catalytic Residues Roles

Residue Roles
Lys8A transition state stabiliser
Lys217A transition state stabiliser
Asp162A steric role, activator
Gly11A (main-N) transition state stabiliser
Gly45A (main-N) transition state stabiliser

Chemical Components

Step 1.

Contributors

Alex Gutteridge, Craig Porter, Gemma L. Holliday