Biology:Dissimilatory sulfite reductase
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| dissimilatory sulfite reductase | |||||||||
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| Identifiers | |||||||||
| EC number | 1.8.99.5 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
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Dissimilatory sulfite reductase (EC 1.8.99.5) is an enzyme that participates in sulfur metabolism in dissimilatory sulfate reduction.[1]
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]
Reaction in organisms performing dissimilatory sulfate reduction:
- (1) sulfite + a [DsrC protein]-dithiol + 2 reduced acceptor + 2 H+ = hydrogen sulfide + a [DsrC protein]-disulfide + 2 acceptor + 3 H2O (overall reaction)
- (1a) sulfite + a [DsrC protein]-dithiol + 2 reduced acceptor + 2 H+ = a [DsrC protein]-S-sulfanyl-L-cysteine + 2 acceptor + 3 H2O
- (1b) a [DsrC protein]-S-sulfanyl-L-cysteine = hydrogen sulfide + a [DsrC protein]-disulfide
Reaction in organisms performing sulfur oxidation:
- (2) a [DsrC protein]-S-sulfanyl-L-cysteine + 3 acceptor + 3 H2O = sulfite + a [DsrC protein]-disulfide + 3 reduced acceptor + 2 H+ (overall reaction)
- (2a) a [DsrC protein]-S-sulfanyl-L-cysteine + 3 acceptor + 3 H2O = a [DsrC]-S-sulfo-L-cysteine + 3 reduced acceptor + H+
- (2b) a [DsrC]-S-sulfo-L-cysteine = sulfite + a [DsrC protein]-disulfide
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.
References
- ↑ "Reaction cycle of the dissimilatory sulfite reductase from Archaeoglobus fulgidus". Biochemistry 49 (41): 8912–21. October 2010. doi:10.1021/bi100781f. PMID 20822098.
- ↑ "Siroheme sulfite reductase isolated from Chromatium vinosum. Purification and investigation of some of its molecular and catalytic properties". Archives of Microbiology 121 (1): 29–36. 1979. doi:10.1007/BF00409202.
- ↑ "The crystal structure of Desulfovibrio vulgaris dissimilatory sulfite reductase bound to DsrC provides novel insights into the mechanism of sulfate respiration". The Journal of Biological Chemistry 283 (49): 34141–9. December 2008. doi:10.1074/jbc.M805643200. PMID 18829451.
- ↑ "A protein trisulfide couples dissimilatory sulfate reduction to energy conservation". Science 350 (6267): 1541–5. December 2015. doi:10.1126/science.aad3558. PMID 26680199. Bibcode: 2015Sci...350.1541S.
- ↑ "The "bacterial heterodisulfide" DsrC is a key protein in dissimilatory sulfur metabolism". Biochimica et Biophysica Acta (BBA) - Bioenergetics 1837 (7): 1148–64. July 2014. doi:10.1016/j.bbabio.2014.03.007. PMID 24662917.
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