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CSA entry for 1eu1
Original Entry
Title:
Oxidoreductase
Compound:
Dimethyl sulfoxide reductase
Mutant:
No
UniProt/Swiss-Prot:
Q57366-DMSA_RHOSH
EC Class:
1.8.99.-
Other CSA Entries:
Overview of all sites for 1eu1
Homologues of 1eu1
Entries for UniProt/Swiss-Prot: Q57366
Entries for EC: 1.8.99.-
Other Databases:
PDB entry: 1eu1
PDBsum entry: 1eu1
UniProt/Swiss-Prot: Q57366
IntEnz entry: 1.8.99.-
Literature Report:
Introduction:
The molybdoenzyme dimethylsulfoxide (DMSO) reductase contributes to the release of dimethylsulfide, a compound that has been implicated in cloud nucleation and global climate regulation. Terminal reductase during anaerobic growth on various sulfoxide and N-oxide compounds. This enzyme contains a mononuclear
Mo coordinated by two molybdopterin guanine dinucleotides as its single cofactor.
Mechanism:
The active site of DMSO reductase contains a mononuclear Mo coordinated by two molybdopterin guanine dinucleotides and the oxygen of Ser147as its single cofactor.

The oxidative half cycle of the reaction is initiated by substrate binding to the reduced enzyme, forming the Ered.DMSO complex containing Mo(IV). This is stabilised by Y114. Binding of DMSO is via the oxygen and leads to some degree of lengthening of the S-O bond. In the catalytic step, the substrate oxygen is transferred as an oxo ligand to the Mo with a concomitant two-electron oxidation of the metal forming Mo(VI) and dimethyl sulfate which is then released from the active site.

The reductive half cycle of the reaction consists of two one-electron reduction steps coupled to the transfer of two protons to generate H2O from the substrate derived oxo group. This reduces Mo(VI) to Mo(IV) . The water is lost to the solvent and the oxidised enzyme is therefore returned to its initial reduced state.

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Literature reference 

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
3000 0
ElectrostaticTransition state
ElectrostaticSubstrate
From the initial Mo(IV) the metal centre coordinates DMSO forming Mo(IV). It then abstracts the O from DMSO forming DMS. Mo(IV) is then reduced to the initial Mo(IV) by electron transfer.
Evidence from paper Evidence concerns Evidence type
PubMed ID 17361996 Current protein Residue is positioned appropriately (ligand position known)
PubMed ID 17921142 Related protein: UniProt Q52675 Residue is covalently bound to intermediate, based on structural data
PubMed ID 17361996 Current protein Residue is covalently bound to intermediate, based on structural data
PubMed ID 17921142 Related protein: UniProt Q52675 Kinetic studies
PubMed ID 17921142 Related protein: UniProt Q52675 Ligand is essential for catalysis
PubMed ID 17361996 Current protein Ligand is essential for catalysis
PubMed ID 17921142 Related protein: UniProt Q52675 Residue is positioned appropriately (ligand position known)

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
TYRA 114 156Sidechain
ElectrostaticTransition state
Stabilises the intermediate Ered.DMSO complex by hydrogen bonding to the O atom.
Evidence from paper Evidence concerns Evidence type
PubMed ID 17921142 Related protein: UniProt Q52675 Residue is positioned appropriately (ligand position known)
PubMed ID 17361996 Current protein Residue is positioned appropriately (ligand position known)
PubMed ID 17921142 Related protein: UniProt Q52675 Mutagenesis of residue
PubMed ID 17361996 Current protein Conservation of residue
PubMed ID 17921142 Related protein: UniProt Q52675 Structural similarity to homologue of known mechanism
PubMed ID 17921142 Related protein: UniProt Q52675 Kinetic studies
PubMed ID 17921142 Related protein: UniProt Q52675 Conservation of residue

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
TRPA 116 158Sidechain
Steric hindranceWater
Prevents water binding to Mo causing loss of the Q pterin group leading to inactivation of the enzyme
Evidence from paper Evidence concerns Evidence type
PubMed ID 17921142 Related protein: UniProt Q52675 Kinetic studies
PubMed ID 17921142 Related protein: UniProt Q52675 Conservation of residue
PubMed ID 17921142 Related protein: UniProt Q52675 Mutagenesis of residue
Notes:
Some finer points of the Enzyme-DMSO complex are still under investigation. The existence of significant S-O bond lengthening during binding is under dispute.

References:
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