Mannonate dehydratase (uxuA)

 

Mannonate dehydratase (uxuA) converts D-mannonate to 2-dehydro-3-deoxy-D-gluconate. In contrast to the Enolase Superfamily equivalogue, this enzyme is dependent on a divalent iron cation. This protein is a member of the Xylose Isomerase-Like superfamily.

 

Reference Protein and Structure

Sequence
P24215 UniProt (4.2.1.8) IPR004628 (Sequence Homologues) (PDB Homologues)
Biological species
Escherichia coli K-12 (Bacteria) Uniprot
PDB
4eay - Crystal structures of mannonate dehydratase from Escherichia coli strain K12 complexed with D-mannonate (2.35 Å) PDBe PDBsum 4eay
Catalytic CATH Domains
3.20.20.150 CATHdb (see all for 4eay)
Cofactors
Iron(3+) (1)
Click To Show Structure

Enzyme Reaction (EC:4.2.1.8)

D-mannonate
CHEBI:17767ChEBI
→
2-dehydro-3-deoxy-D-gluconate
CHEBI:57990ChEBI
+
water
CHEBI:15377ChEBI
Alternative enzyme names: D-mannonate hydrolyase, Altronate hydrolase, Altronic hydro-lyase, Mannonate hydrolyase, Mannonic hydrolase, D-mannonate hydro-lyase,

Enzyme Mechanism

Introduction

His311 abstracts the proton alpha to the carboxylate group (C2) to generate the stabilised enediolate intermediate. The vinylogous syn-elimination of the 3-OH is catalysed by Tyr368 and the following ketonisation with retention of configuration to generate the 2-keto-3-deoxy-D-gluconate product is probably catalysed by both Tyr368 and His311.

Catalytic Residues Roles

UniProt PDB* (4eay)
His352, Tyr368 His352(372)A, Tyr368(388)A Acts as a general acid/base. proton acceptor, proton donor
His298, Asp351, Cys271, His233 His298(318)A, Asp351(371)A, Cys271(291)A, His233(253)A Forms part of the metal 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

proton transfer, overall reactant used, assisted keto-enol tautomerisation, dehydration, overall product formed, unimolecular elimination by the conjugate base, inferred reaction step, native state of enzyme regenerated

References

  1. Zhang Q et al. (2009), J Bacteriol, 191, 5832-5837. Crystal structures of Streptococcus suis mannonate dehydratase (ManD) and its complex with substrate: genetic and biochemical evidence for a catalytic mechanism. DOI:10.1128/JB.00599-09. PMID:19617363.
  2. Dreyer JL (1987), Eur J Biochem, 166, 623-630. The role of iron in the activation of mannonic and altronic acid hydratases, two Fe-requiring hydro-lyases. PMID:3038546.

Step 1. His311 abstracts a proton from the substrate in an assisted keto-enol tautomerisation.

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Catalytic Residues Roles

Residue Roles
Asp351(371)A metal ligand
His233(253)A metal ligand
Cys271(291)A metal ligand
His298(318)A metal ligand
His352(372)A proton acceptor

Chemical Components

proton transfer, overall reactant used, assisted keto-enol tautomerisation

Step 2. Water is eliminated with concomitant deprotonation of Tyr368.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Asp351(371)A metal ligand
His233(253)A metal ligand
Cys271(291)A metal ligand
His298(318)A metal ligand
Tyr368(388)A proton donor

Chemical Components

dehydration, overall product formed, proton transfer, assisted keto-enol tautomerisation, ingold: unimolecular elimination by the conjugate base

Step 3. Inferred step in which the enol intermediate rearranges to form the 2-keto-3-deoxygluconate product and return the enzyme active site to its starting state.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Asp351(371)A metal ligand
His233(253)A metal ligand
Cys271(291)A metal ligand
His298(318)A metal ligand
His352(372)A proton donor
Tyr368(388)A proton acceptor

Chemical Components

inferred reaction step, assisted keto-enol tautomerisation, proton transfer, native state of enzyme regenerated, overall product formed
Download: Image, Marvin File

Step 1. His311 abstracts a proton from the substrate in an assisted keto-enol tautomerisation.

Step 2. Water is eliminated with concomitant deprotonation of Tyr368.

Step 3. Inferred step in which the enol intermediate rearranges to form the 2-keto-3-deoxygluconate product and return the enzyme active site to its starting state.

Products.

Contributors

Gemma L. Holliday