Enoyl-[acyl-carrier-protein] reductase (NADH)

 

Enoyl ACP reductase catalyses the last step in fatty acid biosynthesis. Therefore it is a potential target for antibacterial agent development. It catalyses the NAD(P)H-dependent reduction of enoyl acyl carrier protein.

The bacterial form of the enzyme is different from the human form as it exists as a free globular protein rather than a part of a multienzyme complex. EACPR's show homology, and similarity to hydroxysteroid dehydrogenase, and also beta-keto reductase, suggesting divergent evolution has played a role in the development of the pathway of lipid biosynthesis.

 

Reference Protein and Structure

Sequence
P0AEK4 UniProt (1.3.1.9) IPR014358 (Sequence Homologues) (PDB Homologues)
Biological species
Escherichia coli K-12 (Bacteria) Uniprot
PDB
1qsg - CRYSTAL STRUCTURE OF ENOYL REDUCTASE INHIBITION BY TRICLOSAN (1.75 Å) PDBe PDBsum 1qsg
Catalytic CATH Domains
3.40.50.720 CATHdb (see all for 1qsg)
Click To Show Structure

Enzyme Reaction (EC:1.3.1.9)

O-[S-(2E)-2-enoylpantetheine-4'-phosphoryl]-L-serine(1-) residue
CHEBI:78784ChEBI
+
hydron
CHEBI:15378ChEBI
+
NADH(2-)
CHEBI:57945ChEBI
→
O-(S-2,3-saturated acylpantetheine-4'-phosphoryl)serine(1-) residue
CHEBI:78785ChEBI
+
NAD(1-)
CHEBI:57540ChEBI
Alternative enzyme names: NADH-enoyl acyl carrier protein reductase, NADH-specific enoyl-ACP reductase, Enoyl-ACP reductase, Enoyl-[acyl carrier protein] reductase, Acyl-[acyl-carrier-protein]:NAD(+) oxidoreductase, FabI (gene name), InhA (gene name),

Enzyme Mechanism

Introduction

The catalytic mechanism involves C3 of the substrate being subject to hydride attack by NADH, a bound cofactor. Formation of an enolate intermediate follows, which accepts a proton from Tyr 156. A role in transition state stabilisation through hydrogen bonding has also been suggested for Tyr 156. The enol product would then tautomerise to give the reduced acyl product. Tyr 156 therefore acts as the base that donates the proton to the enolate anion, and Lys 163 acts to stabilise the negatively charged transition state.

Catalytic Residues Roles

UniProt PDB* (1qsg)
Tyr156 Tyr156(159)A The OH group of the tyrosine forms a hydrogen bond to the oxygen of the enolate intermediate, to allow hydride transfer from the cofactor to the substrate. The proton of the OH group is then donated to the substrate to form the enol form of the product. proton acceptor, proton donor
Lys163 Lys163(166)A The positive form of the lysine residue acts to stabilise the enolate intermediate to allow hydride transfer from the cofactor to the substrate to take place. 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

michael addition, proton transfer, hydride transfer, overall reactant used, cofactor used, keto-enol tautomerisation, overall product formed, native state of enzyme regenerated

References

  1. Parikh S et al. (1999), Biochemistry, 38, 13623-13634. Roles of Tyrosine 158 and Lysine 165 in the Catalytic Mechanism of InhA, the Enoyl-ACP Reductase fromMycobacterium tuberculosis†. DOI:10.1021/bi990529c. PMID:10521269.
  2. Seefeld MA et al. (2003), J Med Chem, 46, 1627-1635. Indole Naphthyridinones as Inhibitors of Bacterial Enoyl-ACP Reductases FabI and FabK. DOI:10.1021/jm0204035. PMID:12699381.
  3. Marcinkeviciene J et al. (2001), Arch Biochem Biophys, 390, 101-108. Enoyl-ACP Reductase (FabI) of Haemophilus influenzae: Steady-State Kinetic Mechanism and Inhibition by Triclosan and Hexachlorophene. DOI:10.1006/abbi.2001.2349. PMID:11368521.
  4. Ward WH et al. (1999), Biochemistry, 38, 12514-12525. Kinetic and Structural Characteristics of the Inhibition of Enoyl (Acyl Carrier Protein) Reductase by Triclosan‡. DOI:10.1021/bi9907779. PMID:10493822.
  5. Baldock C et al. (1998), J Mol Biol, 284, 1529-1546. The X-ray structure of Escherichia coli enoyl reductase with bound NAD+ at 2.1 Å resolution. DOI:10.1006/jmbi.1998.2271. PMID:9878369.
  6. Rafferty JB et al. (1995), Structure, 3, 927-938. Common themes in redox chemistry emerge from the X-ray structure of oilseed rape (Brassica napus) enoyl acyl carrier protein reductase. DOI:10.1016/s0969-2126(01)00227-1. PMID:8535786.

Step 1. C3 of the substrate is attacked by a hydride from NADH, forming an enolate and NAD. The oxygen of the enolate is protonated by Tyr156 resulting in an enol.

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Catalytic Residues Roles

Residue Roles
Lys163(166)A electrostatic stabiliser
Tyr156(159)A proton donor

Chemical Components

michael addition, proton transfer, hydride transfer, overall reactant used, cofactor used

Step 2. The enol tautomerises to form the product.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Lys163(166)A electrostatic stabiliser
Tyr156(159)A proton acceptor

Chemical Components

keto-enol tautomerisation, overall product formed, native state of enzyme regenerated
Download: Image, Marvin File

Step 1. C3 of the substrate is attacked by a hydride from NADH, forming an enolate and NAD. The oxygen of the enolate is protonated by Tyr156 resulting in an enol.

Step 2. The enol tautomerises to form the product.

Products.

Contributors

Henry Pertinez, Peter Sarkies, Gemma L. Holliday, Amelia Brasnett