UDP-N-acetylglucosamine pyrophosphorylase

 

The bifunctional enzyme GlmU is able to catalyse two steps in the pathway of bacterial cell wall synthesis:

  1. The C-terminal domain converts glucosamine-1-phosphate to N-acetyl glucosamine-1-phosphate using Acetyl CoA as the donor
  2. The N-terminal domain (this entry) utilises UTP to activate the N-acetyl glucosamine-1-phosphate forming UDP-acetyl-glucosamine and pyrophosphate.

Interest in the processes catalysed by this enzyme stems from its potential as an antibiotic target.

 

Reference Protein and Structure

Sequence
P0ACC7 UniProt (2.3.1.157, 2.7.7.23) IPR025877 (Sequence Homologues) (PDB Homologues)
Biological species
Escherichia coli K-12 (Bacteria) Uniprot
PDB
1hv9 - STRUCTURE OF E. COLI GLMU: ANALYSIS OF PYROPHOSPHORYLASE AND ACETYLTRANSFERASE ACTIVE SITES (2.1 Å) PDBe PDBsum 1hv9
Catalytic CATH Domains
3.90.550.10 CATHdb (see all for 1hv9)
Cofactors
Magnesium(2+) (1)
Click To Show Structure

Enzyme Reaction (EC:2.7.7.23)

N-acetyl-alpha-D-glucosamine 1-phosphate(2-)
CHEBI:57776ChEBI
+
hydron
CHEBI:15378ChEBI
+
UTP(4-)
CHEBI:46398ChEBI
→
diphosphate(3-)
CHEBI:33019ChEBI
+
UDP-N-acetyl-alpha-D-glucosamine(2-)
CHEBI:57705ChEBI
Alternative enzyme names: Acetylglucosamine 1-phosphate uridylyltransferase, GlmU uridylyltransferase, UDP-N-acetylglucosamine pyrophosphorylase, UDP-GlcNAc pyrophosphorylase, UDP-acetylglucosamine pyrophosphorylase, UTP:2-acetamido-2-deoxy-alpha-D-glucose-1-phosphate uridylyltransferase, Uridine diphosphate-N-acetylglucosamine pyrophosphorylase, Uridine diphosphoacetylglucosamine phosphorylase, Uridine diphosphoacetylglucosamine pyrophosphorylase, N-acetylglucosamine-1-phosphate uridyltransferase,

Enzyme Mechanism

Introduction

The mechanism of the transfer of UDP to N acetylglucosamine-1-phosphate proceeds via nucleophilic attack from the phosphate oxygen of the phosphate moiety on the alpha phosphate producing a pentavalent phosphate transition state. This is stabilised by Mg2+ at the active site and Arg 18, and collapses to release the beta and gamma phosphates as pyrophosphate.

Catalytic Residues Roles

UniProt PDB* (1hv9)
Arg18 Arg18B Stabilises the transition state by forming electrostatic contacts to the alpha phosphate of UTP. electrostatic 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

overall reactant used, overall product formed, bimolecular nucleophilic substitution, inferred reaction step, proton transfer

References

  1. Brown K et al. (1999), EMBO J, 18, 4096-4107. Crystal structure of the bifunctional N-acetylglucosamine 1-phosphate uridyltransferase from Escherichia coli: a paradigm for the related pyrophosphorylase superfamily. DOI:10.1093/emboj/18.15.4096. PMID:10428949.

Step 1. The phosphate of N-acetyl-alpha-D-glucosamine 1-phosphate attacks the alpha phosphate of UTP. This releases diphosphate and forms the product.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Arg18B electrostatic stabiliser

Chemical Components

overall reactant used, overall product formed, ingold: bimolecular nucleophilic substitution

Step 2. The diphosphate group is protonated. The proton may be sourced from the solvent.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles

Chemical Components

inferred reaction step, proton transfer, overall product formed
Download: Image, Marvin File

Step 1. The phosphate of N-acetyl-alpha-D-glucosamine 1-phosphate attacks the alpha phosphate of UTP. This releases diphosphate and forms the product.

Step 2. The diphosphate group is protonated. The proton may be sourced from the solvent.

Products.

Contributors

Peter Sarkies, Gemma L. Holliday, Amelia Brasnett