Information on EC 1.8.99.5 - dissimilatory sulfite reductase

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The enzyme appears in viruses and cellular organisms

EC NUMBER
COMMENTARY hide
1.8.99.5
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RECOMMENDED NAME
GeneOntology No.
dissimilatory sulfite reductase
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REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
a [DsrC protein]-S-sulfanyl-L-cysteine + 2 acceptor + 3 H2O = sulfite + a [DsrC protein]-dithiol + 2 reduced acceptor + 2 H+
show the reaction diagram
(1b)
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a [DsrC protein]-S-sulfanyl-L-cysteine + 3 acceptor + 3 H2O = a [DsrC]-S-sulfo-L-cysteine + 3 reduced acceptor + H+
show the reaction diagram
(2a)
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a [DsrC protein]-S-sulfanyl-L-cysteine + 3 acceptor + 3 H2O = sulfite + a [DsrC protein]-disulfide + 3 reduced acceptor + 2 H+
show the reaction diagram
(2), overall reaction
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a [DsrC]-S-sulfo-L-cysteine = sulfite + a [DsrC protein]-disulfide
show the reaction diagram
(2b)
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hydrogen sulfide + a [DsrC protein]-disulfide + 2 acceptor + 3 H2O = sulfite + a [DsrC protein]-dithiol + 2 reduced acceptor + 2 H+
show the reaction diagram
hydrogen sulfide + a [DsrC protein]-disulfide = a [DsrC protein]-S-sulfanyl-L-cysteine
show the reaction diagram
(1a)
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
sulfate reduction IV (dissimilatory, to hydrogen sufide))
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sulfate reduction V (dissimilatory, to thiosulfate)
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superpathway of tetrathionate reduction (Salmonella typhimurium)
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superpathway of thiosulfate metabolism (Desulfovibrio sulfodismutans)
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non-pathway related
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Nitrotoluene degradation
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Sulfur metabolism
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Metabolic pathways
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Microbial metabolism in diverse environments
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SYSTEMATIC NAME
IUBMB Comments
hydrogen-sulfide:[DsrC sulfur-carrier protein],acceptor oxidoreductase
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.
ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
O33998, i.e. subunit DsrA, D3RSN2 i.e. subunit DsrB
O33998 and D3RSN2
UniProt
Manually annotated by BRENDA team
O93650 i.e. subunit DsrA, O93651 i.e. subunit DsrB
O93650 and O93651
UniProt
Manually annotated by BRENDA team
O93650 i.e. subunit DsrA, O93651 i.e. subunit DsrB
O93650 and O93651
UniProt
Manually annotated by BRENDA team
Q9ZH18 i.e. subunit DsrA, Q9ZH17 i.e. subunit DsrB
Q9ZH18 and Q9ZH17
UniProt
Manually annotated by BRENDA team
subunit DsrC
UniProt
Manually annotated by BRENDA team
subunit DsrC
UniProt
Manually annotated by BRENDA team
O33909 i.e. subunit DsrA, O33910 i.e. subunit DsrB
O33909 and O33910
UniProt
Manually annotated by BRENDA team
Soil bacterium
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Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
evolution
MccA belongs to the genetically diverse family of multiheme c enzymes and has eight heme groups covalently attached to conserved heme-binding motifs in the peptide sequence. Multiheme cytochrome c enzymes show a high conservation of heme group arrangements, but not of sequence, with recurring heme-packing motifs that result in either a parallel or a perpendicular packing of two of the moieties. They catalyse complexmulti-electron redox reactions and bind their substrates through the free electron pairs of a heteroatom to a free coordination position at an active-site hem group. Electrons are then provided or accepted by the tightly coupled chain of heme groups
metabolism
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DsrC is a key protein in dissimilatory sulfite reduction
physiological function
additional information
anoxically purified MccA exhibits a 2 to 5.5fold higher specific sulfite reductase activity than the enzyme isolated under oxic conditions. Presence of two cysteine residues, C399 and C495, juxtaposed at the distal side of the active-site cavity. The active site is a shallow cavity on the distal side of heme 2, lined by residues K208, Y285, Y301, R366 and K393, which are conserved among MccA orthologues
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
hydrogen sulfide + a [DsrC protein]-disulfide + acceptor + H2O
sulfite + a [DsrC protein]-dithiol + reduced acceptor + H+
show the reaction diagram
hydroxylamine + a [DsrC protein]-dithiol + 2 reduced acceptor + 2 H+
? + a [DsrC protein]-disulfide + 2 acceptor + 3 H2O
show the reaction diagram
nitrite + a [DsrC protein]-dithiol + 2 reduced acceptor
? + a [DsrC protein]-disulfide + 2 acceptor + 2 H2O
show the reaction diagram
SeO32- + a [DsrC protein]-dithiol + 2 reduced methyl viologen + 2 H+
HSe- + a [DsrC protein]-disulfide + 2 oxidized methyl viologen + 3 H2O
show the reaction diagram
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40% of the activity with sulfite
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?
sulfite + 6 ferrocytochrome c + 6 H+
sulfide + 6 ferricytochrome c + 3 H2O
show the reaction diagram
overall transfer of 6 electrons during the reaction
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-
?
sulfite + a [DsrC protein]-dithiol + 2 reduced ferredoxin + 2 H+
hydrogen sulfide + a [DsrC protein]-disulfide + 2 oxidized ferredoxin + 3 H2O
show the reaction diagram
sulfite + a [DsrC protein]-dithiol + reduced methyl viologen
trithionate + a [DsrC protein]-disulfide + oxidized methyl viologen
show the reaction diagram
additional information
?
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
hydrogen sulfide + a [DsrC protein]-disulfide + acceptor + H2O
sulfite + a [DsrC protein]-dithiol + reduced acceptor + H+
show the reaction diagram
sulfite + 6 ferrocytochrome c + 6 H+
sulfide + 6 ferricytochrome c + 3 H2O
show the reaction diagram
Q7MSJ8
overall transfer of 6 electrons during the reaction
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?
additional information
?
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Q7MSJ8
multiheme cytochrome c enzymes catalyse complex-multi-electron redox reactions and bind their substrates through the free electron pairs of a heteroatom to a free coordination position at an active-site hem group. Electrons are then provided or accepted by the tightly coupled chain of heme groups
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
cytochrome c
octaheme cytochrome
heme
octaheme cytochrome, a homotrimer with an unprecedented fold and heme arrangement, as well as a heme bound to a CX15CH motif. The heterobimetallic active-site heme 2 has a Cu(I) ion juxtaposed to a heme c at a Fe-Cu distance of 4.4 A, active-site heme 2 is bound to a canonical CXXCH motif with H306 as a proximal axial ligand. In the CX15CH motif of heme 8, the extended region between the two cysteine residues forms a loop with a short helical turn, in direct vicinity to another loop harbouring the only non-proline cis peptide in the enzyme, between residues G508 and F509. Its formation might require the essential peptidyl isomerase MccB2, and it is presumed to be a prerequisite for correct folding of the loop in the maturation process of heme 8, which is likely to be attached by the dedicated cytochrome c synthase CcsA1. The structure of the CX15CH heme c binding motif disrupts the general parallel/perpendicular heme stacking sequence, and rotates the heme out of plane, possibly to optimize the interaction with the putative electron donor, the iron-sulfur protein MccC
siroheme
[4Fe-4S]-center
additional information
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no activity is observed with NAD, NADP, FAD or FMN
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Cu
the heterobimetallic active-site heme 2 has a Cu(I) ion juxtaposed to a heme c at a Fe-Cu distance of 4.4 A. While the combination of metals is reminiscent of respiratory heme–copper oxidases, the oxidation-labile Cu(I) centre of MccA does not seem to undergo a redox transition during catalysis. The copper-depleted form II of MccA, the absence of the heterometal allows for a binding mode of sulfite that is similar to the one seen in the siroheme-containing enzymes or in NrfA. In the structure of the Cu-containing, high-activity form I of MccA, all 12 monomers in the asymmetric unit have a ligand bound to heme 2
Fe
the heterobimetallic active-site heme 2 has a Cu(I) ion juxtaposed to a heme c at a Fe-Cu distance of 4.4 A
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
KCN
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1 mM, complete inhibition
NaN3
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1 mM, 18% inhibition
Tris/HCl
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Tris buffer has an inhibitory effect. Approximately 60% less activity than with phosphate buffer is obtained at pH 7.5
additional information
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not inhibitory: iodoacetate
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
48
hydroxylamine
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pH 7.6, 22°C
0.028
nitrite
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pH 7.6, 22°C
0.06 - 3.1
sulfite
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
29
hydroxylamine
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pH 7.6, 22°C
0.038
nitrite
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pH 7.6, 22°C
0.31
sulfite
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pH 7.6, 22°C
kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.6
hydroxylamine
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pH 7.6, 22°C
1.4
nitrite
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pH 7.6, 22°C
5.17
sulfite
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pH 7.6, 22°C
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
pI VALUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
5.3
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isoelectric focusing
8.4
O33909 and O33910
isoelectric focusing
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
PDB
SCOP
CATH
ORGANISM
UNIPROT
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Desulfomicrobium norvegicum (strain DSM 1741 / NCIMB 8310)
Desulfovibrio vulgaris (strain Hildenborough / ATCC 29579 / DSM 644 / NCIMB 8303)
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
11000
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2 * 50000, alpha-subunit, + 2 * 45000, beta subunit, + 1-3 * 11000, gamma-subunit. The gamma-subunit seems not to be an integral part of the protein
12700
x * 12700, subunit DsrC, claculated
13400
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2 * 13400 plus 2 * 28400, SDS-PAGE
28400
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2 * 13400 plus 2 * 28400, SDS-PAGE
41200
O33909 and O33910
2 * 44200, alpha-subunit, + 2 * 41200, beta-subunit
44200
O33909 and O33910
2 * 44200, alpha-subunit, + 2 * 41200, beta-subunit
45000
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2 * 50000, alpha-subunit, + 2 * 45000, beta subunit, + 1-3 * 11000, gamma-subunit. The gamma-subunit seems not to be an integral part of the protein
48000
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2 * 48000, alpha-subunit, 2 * 48000, beta-subunit, SDS-PAGE and N-terminal sequencing
50000
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2 * 50000, alpha-subunit, + 2 * 45000, beta subunit, + 1-3 * 11000, gamma-subunit. The gamma-subunit seems not to be an integral part of the protein
70000
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MalPEG-labelled enzyme, gel filtration
165000
O33909 and O33910
PAGE
167000
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sedimentation equilibrium centrifugation
170000
O33909 and O33910
gel filtration
200000
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gel filtration, both enzyme from membrane and soluble fraction
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
heterotetramer
homodimer
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2 * 35000, MalPEG-labelled enzyme, SDS-PAGE
homotrimer
with an unprecedented fold and heme arrangement, three-dimensional structure analysis
multimer
tetramer
O33909 and O33910
2 * 44200, alpha-subunit, + 2 * 41200, beta-subunit
additional information
in the CX15CH motif of heme 8, the extended region between the two cysteine residues forms a loop with a short helical turn, in direct vicinity to another loop harbouring the only non-proline cis peptide in the enzyme, between residues G508 and F509. Its formation might require the essential peptidyl isomerase MccB2, and it is presumed to be a prerequisite for correct folding of the loop in the maturation process of heme 8, which is likely to be attached by the dedicated cytochrome c synthase CcsA1. The structure of the CX15CH heme c binding motif disrupts the general parallel/perpendicular heme stacking sequence, and rotates the heme out of plane, possibly to optimize the interaction with the putative electron donor, the iron-sulfur protein MccC
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
modeling of three dimensional strucuture of the alpha2beta2 hetero-tetrameric protein complex
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crystal structure at 2 A resolution and comparison with that of the phylogenetically related assimilatory sulfite reductase aSir. Dissimilatory sulfite reductase dSir is organized as a heterotetrameric complex composed of two catalytically independent alphabeta heterodimers. aSir is a monomeric protein built of two fused modules. aSir binds one siroheme-[4Fe-4S] center, dSir harbors two of them within each alphabeta heterodimer. Only one siroheme-[4Fe-4S] center in each alphabeta heterodimer is catalytically active, whereas access to the second one is blocked by a tryptophan residue
Q59109 and Q59110
structure of gamma-subunit DsrC, native protein to 1.12 A, and in complex with tert-butyl hydroperoxide to 2.1 A resolution. The highly conserved C-terminal arm adopts a well-defined conformation. The disulfide bond between Cys77 and Cys85 connects helices alpha3 and alpha4 and presumably plays a structural role to stabilize the protein
to 1.37 A resolution, space group P41212, with unit-cell parameters a = b = 163.26, c = 435.32 A. The crystal contains three alpha2beta2gamma2 units per asymmetric unit,
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to 2.8 A resolution, space group P21 with unit-cell parameters a = 122.7, b = 119.4 and c = 146.7 A and b =110.0 degrees
solution structure of subunit DsrC adopts a fold consisting of an orthogonal helical bundle with a beta-hairpin along one side. The protein contains two disulfide bonds but remains folded following reduction of the disulfides. A conserved cysteine next to the C-terminus is located on a seven-residue C-terminal arm that is not part of the globular protein
purified enzyme, X-ray diffraction structure determination and analysis at 2.2 A resolution, single-wavelength anomalous dispersion
TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
70
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stable up to, rapidly denatures above
Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
both from membrane and soluble fraction
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HiTrap chelating column chromatography
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Q sepharose column chromatography
Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
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Q59109 and Q59110
expressed in Escherichia coli BL21gold(DE3) cells
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structure with the alpha and beta subunits bound to the DsrC protein. The alpha2beta2gamma2 assembly contains two siroheme-[4Fe4S] cofactors bound by DsrB, two sirohydrochlorins and two [4Fe-4S]-centers bound by DsrA, and another four [4Fe-4S]-centers in the ferredoxin domains. A sulfite molecule, coordinating the siroheme, is found at the active site. The DsrC protein is bound in a cleft between DsrA and DsrB with its conserved C-terminal cysteine reaching the distal side of the siroheme. The process of sulfite reduction may involve DsrAB, DsrC, and the DsrMKJOP membrane complex (a membrane complex with putative disulfide/thiol reductase activity), in which two of the six electrons for reduction of sulfite derive from the membrane quinone pool
P45574 and P45575
Show AA Sequence (146 entries)
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