ID 1.8.99.5 DE dissimilatory sulfite reductase. AN siroheme sulfite reductase. CA (1) [DsrC protein]-disulfide + 2 A + 3 H2O + hydrogen sulfide = CA [DsrC protein]-dithiol + 2 AH2 + H(+) + sulfite. CA (2) [DsrC protein]-S-sulfanyl-L-cysteine/L-cysteine + 3 A + 3 H2O = CA [DsrC protein]-disulfide + 3 AH2 + 2 H(+) + sulfite. CC -!- The enzyme is essential in prokaryotic sulfur-based energy CC metabolism, including sulfate/sulfite reducing organisms, sulfur- CC oxidizing bacteria, and organosulfonate reducers. CC -!- In sulfur reducers it catalyzes the reduction of sulfite to sulfide, CC while in sulfur oxidizers it catalyzes the opposite reaction. CC -!- The reaction involves the small protein DsrC, which is present in all CC the organisms that contain dissimilatory sulfite reductase. CC -!- During the process an intramolecular disulfide bond is formed between CC two L-cysteine residues of DsrC. CC -!- This disulfide can be reduced by a number of proteins including DsrK CC and TcmB. CC -!- This enzyme is different from EC 1.8.1.2 and EC 1.8.7.1, which are CC involved in sulfate assimilation. CC -!- Formerly EC 1.8.99.3. DR O33998, DSRA_ALLVD ; Q59109, DSRA_ARCFU ; Q59110, DSRB_ARCFU ; DR P45575, DSVB_DESVH ; P94694, DSVB_MEGG1 ; P45573, DSVC_DESVH ; //