Dissimilatory sulfite reductase
Class of enzymes
From Wikipedia, the free encyclopedia
Dissimilatory sulfite reductase (EC 1.8.1.22) is an enzyme that participates in sulfur metabolism in dissimilatory sulfate reduction.[1]
| dissimilatory sulfite reductase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC no. | 1.8.1.22 | ||||||||
| Databases | |||||||||
| BRENDA | enzyme data | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | enzyme entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| Rhea | reactions | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
| |||||||||
The enzyme is essential in prokaryotic sulfur-based energy metabolism, including sulfate/sulfite reducing organisms, sulfur-oxidizing bacteria, and organosulfonate reducers. In sulfur reducers, it catalyses the reduction of sulfite to sulfide (reaction 1); while in sulfur oxidizers, it catalyses the opposite reaction (reaction 2).[2] The reaction involves the small protein DsrC, which is present in all the organisms that contain dissimilatory sulfite reductase.[3] During the process, an intramolecular trisulfide is formed between two L-cysteine residues of DsrC and the sulfur atom from sulfite.[4] This trisulfide can be reduced by a number of proteins including DsrK and TcmB.[5]
DsrAB has been found in 32 bacterial and 4 to 5 archaeal phyla.[6] DsrA and DsrC have been found as auxiliary metabolic genes in bacteriophages.[7]
Reaction in organisms performing dissimilatory sulfate reduction:
SO2−3 + [DsrC]-(SH)2 + 2 acceptorred + 2H+ → H2S + [DsrC]-S2 + 2 acceptorox + 3H2O
[DsrC]-Cys-S-HS* → H2S + [DsrC]-S2
Reaction in organisms performing sulfur oxidation:
[DsrC]-Cys-S-HS* + 3 acceptorox + 3H2O → SO2−3 + [DsrC]-S2 + 3 acceptorred + 2H+
[DsrC]-Cys-S-HS* + 3 acceptorox + 3H2O → [DsrC]-Cys-S-SO3 + 3 acceptorred + H+
[DsrC]-Cys-S-SO3 → SO2−3 + [DsrC]-S2 + H+
The systematic name of this enzyme class is hydrogen-sulfide:[DsrC sulfur-carrier protein],acceptor oxidoreductase.
This enzyme is different from EC 1.8.1.2 – assimilatory sulfite reductase (NADPH), and EC 1.8.7.1 – assimilatory sulfite reductase (ferredoxin), which are involved in sulfate assimilation.
