L-fuconate dehydratase
L-fuconate dehydratase is a member of the enolase superfamily and is known to play a role in the catabolism of L-fucose. It catalyses the dehydration of L-fuconate to 2-keto-3-deoxy-L-fuconate by the abstraction of the proton alpha to the carboxylate group of the substrate to generate an enediolate intermediate that is stabilised by an essential magnesium ion.
Reference Protein and Structure
- Sequence
-
Q8P3K2
(4.2.1.68)
(Sequence Homologues) (PDB Homologues)
- Biological species
-
Xanthomonas campestris pv. campestris str. ATCC 33913 (Bacteria)
- PDB
-
2hxt
- Crystal structure of L-Fuconate Dehydratase from Xanthomonas campestris liganded with Mg++ and D-erythronohydroxamate
(1.7 Å)
- Catalytic CATH Domains
-
3.20.20.120
(see all for 2hxt)
- Cofactors
- Magnesium(2+) (1)
Enzyme Mechanism
Introduction
This enzyme follows the classical enolase superfamily mechanism in which Lys220 abstracts proton from the carbon alpha to the carboxylate group. A beta elimination then occurs to produce water and deprotonated His351. The intermediate then undergoes a keto-enol tautomerisation assisted by His351 and to generate the final product and Lys220.
Catalytic Residues Roles
UniProt | PDB* (2hxt) | ||
His351 | His351A | Acts as a general acid/base. This residue is responsible for the donation of a proton to the leaving water molecule. | proton acceptor, proton donor |
Asp324 | Asp324A | Modifies the pKa of the catalytic histidine residue. | metal ligand |
Lys220 | Lys220A | Acts as a general acid/base. This is the residue responsible for the initial alpha proton abstraction. | proton acceptor, proton donor |
Glu301, Asp248, Glu274 | Glu301A, Asp248A, Glu274A | Forms part of the magnesium binding site. | metal ligand |
Chemical Components
proton transfer, overall product formed, assisted keto-enol tautomerisation, dehydration, unimolecular elimination by the conjugate base, native state of enzyme regeneratedReferences
- Yew WS et al. (2006), Biochemistry, 45, 14582-14597. Evolution of enzymatic activities in the enolase superfamily: L-fuconate dehydratase from Xanthomonas campestris. DOI:10.1021/bi061687o. PMID:17144652.
Catalytic Residues Roles
Residue | Roles |
---|---|
Asp324A | metal ligand |
Glu274A | metal ligand |
Glu301A | metal ligand |
Asp248A | modifies pKa |
Lys220A | proton acceptor |
Chemical Components
proton transfer, overall product formed, assisted keto-enol tautomerisationStep 2. A beta elimination produces water with concomitant deprotonation of His351.
Download: Image, Marvin FileCatalytic Residues Roles
Residue | Roles |
---|---|
Asp324A | metal ligand |
Glu274A | metal ligand |
Glu301A | metal ligand |
Asp248A | modifies pKa |
His351A | proton donor |
Chemical Components
dehydration, overall product formed, ingold: unimolecular elimination by the conjugate base, proton transferStep 3. His351 abstracts a proton from the intermediate OH group on the carbon alpha to the carboxylate in an assisted keto-enol tautomerisation with concomitant deprotonation of Lys220.
Download: Image, Marvin FileCatalytic Residues Roles
Residue | Roles |
---|---|
Asp324A | metal ligand |
Glu274A | metal ligand |
Glu301A | metal ligand |
Asp248A | modifies pKa |
Lys220A | proton donor |
His351A | proton acceptor |