EC Explorer

1.8.99.5

dissimilatory sulfite reductase

(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

siroheme sulfite reductase, hydrogen-sulfide:(acceptor) oxidoreductase (ambiguous), DsrAB

hydrogen-sulfide:[DsrC sulfur-carrier protein],acceptor oxidoreductase

37256-51-2

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.

created 2015