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EC 1.8.99.5 Details
EC number
1.8.99.5
Accepted name
dissimilatory sulfite reductase
Reaction
(1) hydrogen sulfide + a [DsrC protein]-disulfide + 2 acceptor + 3 H2O = sulfite + a [DsrC protein]-dithiol + 2 reduced acceptor + 2 H+ (overall reaction);;(1a) hydrogen sulfide + a [DsrC protein]-disulfide = a [DsrC protein]-S-sulfanyl-L-cysteine;;(1b) a [DsrC protein]-S-sulfanyl-L-cysteine + 2 acceptor + 3 H2O = sulfite + a [DsrC protein]-dithiol + 2 reduced acceptor + 2 H+;;(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
Other name(s)
siroheme sulfite reductase, hydrogen-sulfide:(acceptor) oxidoreductase (ambiguous), DsrAB
Systematic name
hydrogen-sulfide:[DsrC sulfur-carrier protein],acceptor oxidoreductase
CAS registry number
37256-51-2
Comment
Contain siroheme. 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 in the right to left direction), while in sulfur oxidizers it catalyses the opposite reaction (reaction 2 in the left to right direction) [1]. The reaction involves the small protein DsrC, which is present in all the organisms that contain dissimilatory sulfite reductase. During the process an intramolecular disulfide bond is formed between two L-cysteine residues of DsrC. This disulfide can be reduced by a number of proteins including DsrK and TcmB [5]. 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.
History
created 2015
EC Tree
1.1.1.68 created 1965, deleted 1978 [transferred to EC 1.1.99.15, deleted 1980]
1.1.1.70 created 1965, deleted 1978
1.1.1.74 created 1972, deleted 1976
1.1.1.89 created 1972, deleted 1976
1.1.1.109 created 1972, deleted 1976
1.1.1.139 created 1972, deleted 1978
1.1.1.155 created 1976, deleted 2004
1.1.1.171 created 1978, deleted 1984
1.1.1.180 created 1983, deleted 1984
1.1.1.182 created 1983, deleted 1990
1.1.1.204 created 1972 as EC 1.2.1.37, transferred 1984 to EC 1.1.1.204, modified 1989, deleted 2004
1.1.1.242 created 1992, deleted 2001
1.1.1.249 provisional version created 1999, deleted 1999 (reinstated 2001 as EC 2.5.1.46)
1.1.1.253 created 1999, deleted 2003
1.8.99.4 created 1999, deleted 2000