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Literature summary extracted from

  • Wang, J.; Krizowski, S.; Fischer-Schrader, K.; Niks, D.; Tejero, J.; Sparacino-Watkins, C.; Wang, L.; Ragireddy, V.; Frizzell, S.; Kelley, E.E.; Zhang, Y.; Basu, P.; Hille, R.; Schwarz, G.; Gladwin, M.T.
    Sulfite oxidase catalyzes single-electron transfer at molybdenum domain to reduce nitrite to nitric oxide (2015), Antioxid. Redox Signal., 23, 283-294 .
    View publication on PubMedView publication on EuropePMC

Activating Compound

EC Number Activating Compound Comment Organism Structure
1.8.3.1 cytochrome c
-
 Homo sapiens

Cloned(Commentary)

EC Number Cloned (Comment) Organism
1.8.3.1 recombinant expression of wild-type and mutant enzymes in Escherichia coli strain Escherichia coli TP1000 cells, specific replacement of the active site Cys207 with selenocysteine during protein expression in Escherichia coli Homo sapiens

Protein Variants

EC Number Protein Variants Comment Organism
1.8.3.1 C242S/C253S/C260S/C451S site-directed mutagenesis, mutation of the four active site Cys residues Homo sapiens
1.8.3.1 additional information the specific replacement of the active site Cys207 with selenocysteine during protein expression in Escherichia coli. The sulfite oxidizing activity (kcat/KM) of SeSOMD4Ser is increased at least 1.5fold, and the pH optimum is shifted to a more acidic value compared to those of SOMD4Ser and SOMD4Cys(wt) Homo sapiens

KM Value [mM]

EC Number KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
1.8.3.1 additional information
-
 additional information steady-state kinetics Homo sapiens
1.8.3.1 additional information
-
 additional information kinetics of sulfite oxidase-dependent nitrite reduction, the catalyzes single-electron transfer is similar to Michaelis-Menten kinetics Homo sapiens
1.8.3.1 0.004
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 0.0042
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 0.0048
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 0.0062
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 0.0079
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 0.0082
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 0.0096
-
 sulfite with ferricanide, pH 6.0, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 0.0107
-
 sulfite with ferricanide, pH 8.4, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 0.0121
-
 sulfite with ferricanide, pH 6.0, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 0.0146
-
 sulfite with ferricanide, pH 8.4, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 0.0166
-
 sulfite with ferricanide, pH 8.4, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 0.0174
-
 sulfite with ferricanide, pH 8.9, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 0.019
-
 sulfite with ferricanide, pH 6.0, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 0.0196
-
 sulfite with ferricanide, pH 8.9, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 0.0288
-
 sulfite with ferricanide, pH 8.9, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens

Localization

EC Number Localization Comment Organism GeneOntology No. Textmining
1.8.3.1 mitochondrion
-
 Homo sapiens 5739
-

Metals/Ions

EC Number Metals/Ions Comment Organism Structure
1.8.3.1 Fe3+
-
 Homo sapiens
1.8.3.1 Molybdenum
-
 Homo sapiens
1.8.3.1 Molybdenum active site bound to the dithiolene sulfurs of one molybdopterin (MPT) molecule, carrying two oxygen ligands, and is further coordinated by the thiol sulfur of a conserved cysteine residue Homo sapiens
1.8.3.1 additional information the SO Moco binding domain has the ability to oxidize sulfite in the presence of artificial electron acceptors like ferricyanide. The two-electron oxidation of sulfite to sulfate occurs at the molybdenum site, which is reduced from Mo(VI) to Mo(IV), followed by intramolecular electron transfer to the cytb5 site, with cytochrome c serving as the terminal electron acceptor Homo sapiens

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
1.8.3.1 sulfite + O2 + H2O Homo sapiens
-
 sulfate + H2O2
-
 ?
1.8.3.1 sulfite + O2 + H2O Homo sapiens sulfite is the physiological substrate sulfate + H2O2
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
1.8.3.1 Homo sapiens P51687
-
-

Source Tissue

EC Number Source Tissue Comment Organism Textmining
1.8.3.1 fibroblast
-
 Homo sapiens
-

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
1.8.3.1 additional information reduced sulfite oxidase catalyzes single-electron transfer at molybdenum domain to reduce nitrite to nitric oxide. At physiological concentrations of nitrite, sulfite oxidase functions as nitrite reductase in the presence of a one-electron donor, exhibiting redox coupling of substrate oxidation and nitrite reduction to form NO. With sulfite, the physiological substrate, sulfite oxidase only facilitates one turnover of nitrite reduction. Nitrite reduction occurs at the molybdenum center via coupled oxidation of Mo(IV) to Mo(V). Reaction rates of nitrite to NO decreased in the presence of a functional heme domain, mediated by steric and redox effects of this domain. Nitrite binds to and is reduced at the molybdenum site of mammalian sulfite oxidase, which may be allosterically regulated by heme and molybdenum domain interactions, and contributes to the mammalian nitrate-nitrite-NO signaling pathway in human fibroblasts. Using phenosafranine or sulfite as reducing substrate, the Mo-domain shows much faster nitrite reduction to NO than holo-sulfite oxidase, catalytic Mo(IV) to Mo(V) nitrite reduction cycle, overview Homo sapiens ?
-
 ?
1.8.3.1 additional information the sulfite oxidase catalyzes single-electron transfer at molybdenum domain to reduce nitrite to nitric oxide. The SO Moco binding domain has the ability to oxidize sulfite in the presence of artificial electron acceptors like ferricyanide. The two-electron oxidation of sulfite to sulfate occurs at the molybdenum site, which is reduced from Mo(VI) to Mo(IV), followed by intramolecular electron transfer to the cytb5 site, with cytochrome c serving as the terminal electron acceptor. The movement of domains between the Moco domain and the cytb5 domain facilitated by the flexible linker is essential for efficient electron transfer between the heme and the Moco Homo sapiens ?
-
 ?
1.8.3.1 sulfite + ferricyanide + H+
-
 Homo sapiens sulfate + reduced ferricyanide
-
 ?
1.8.3.1 sulfite + O2 + H2O
-
 Homo sapiens sulfate + H2O2
-
 ?
1.8.3.1 sulfite + O2 + H2O sulfite is the physiological substrate Homo sapiens sulfate + H2O2
-
 ?
1.8.3.1 sulfite + O2 + H2O during the sulfite-sulfite oxidase-cytochrome c catalytic cycle, movement between the molybdenum and heme domain is required to enable efficient single-electron transfer from molybdenum via the heme b5 cofactor to cytochrome c Homo sapiens sulfate + H2O2
-
 ?

Synonyms

EC Number Synonyms Comment Organism
1.8.3.1 SUOX
-
 Homo sapiens

Temperature Optimum [°C]

EC Number Temperature Optimum [°C] Temperature Optimum Maximum [°C] Comment Organism
1.8.3.1 25
-
 assay at Homo sapiens
1.8.3.1 25 37 assay at Homo sapiens

Turnover Number [1/s]

EC Number Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
1.8.3.1 9.4
-
 sulfite with ferricanide, pH 6.0, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 13.9
-
 sulfite with ferricanide, pH 6.0, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 16.2
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 19.8
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 20.8
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 25.8
-
 sulfite with ferricanide, pH 8.4, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 26.1
-
 sulfite with ferricanide, pH 6.0, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 27.3
-
 sulfite with ferricanide, pH 8.9, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 31.8
-
 sulfite with ferricanide, pH 8.9, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 32.4
-
 sulfite with ferricanide, pH 8.4, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 36.2
-
 sulfite with ferricanide, pH 8.9, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 37.7
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 41.2
-
 sulfite with ferricanide, pH 8.4, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 46.6
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens

pH Optimum

EC Number pH Optimum Minimum pH Optimum Maximum Comment Organism
1.8.3.1 6
-
 assay at Homo sapiens
1.8.3.1 7.4
-
 assay at Homo sapiens

Cofactor

EC Number Cofactor Comment Organism Structure
1.8.3.1 cytochrome b5
-
 Homo sapiens
1.8.3.1 cytochrome c
-
 Homo sapiens
1.8.3.1 molybdenum cofactor
-
 Homo sapiens
1.8.3.1 additional information during the sulfite-sulfite oxidase-cytochrome c catalytic cycle, movement between the molybdenum and heme domain is required to enable efficient single-electron transfer from molybdenum via the heme b5 cofactor to cytochrome c. Using phenosafranine or sulfite as reducing substrate, the Mo-domain shows much faster nitrite reduction to NO than holo-sulfite oxidase Homo sapiens

General Information

EC Number General Information Comment Organism
1.8.3.1 additional information the catalytic site of SO consists of a molybdenum ion bound to the dithiolene sulfurs of one molybdopterin (MPT) molecule, carrying two oxygen ligands, and is further coordinated by the thiol sulfur of a conserved cysteine residue Homo sapiens
1.8.3.1 physiological function sulfite oxidase (SO) is an essential molybdoenzyme for humans, catalyzing the final step in the degradation of sulfur-containing amino acids and lipids, which is the oxidation of sulfite to sulfate Homo sapiens
1.8.3.1 physiological function sulfite oxidase significantly contributes to hypoxic nitrite signaling as demonstrated by activation of the canonical NO-sGCcGMP pathway Homo sapiens

kcat/KM [mM/s]

EC Number kcat/KM Value [1/mMs-1] kcat/KM Value Maximum [1/mMs-1] Substrate Comment Organism Structure
1.8.3.1 979
-
 sulfite with ferricanide, pH 6.0, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 1139
-
 sulfite with ferricanide, pH 6.0, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 1257
-
 sulfite with ferricanide, pH 8.9, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 1374
-
 sulfite with ferricanide, pH 6.0, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 1615
-
 sulfite with ferricanide, pH 8.9, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 1828
-
 sulfite with ferricanide, pH 8.9, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 1952
-
 sulfite with ferricanide, pH 8.4, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 2411
-
 sulfite with ferricanide, pH 8.4, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 2822
-
 sulfite with ferricanide, pH 8.4, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 3194
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 4050
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 4125
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 4598
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens
1.8.3.1 4952
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme Homo sapiens
1.8.3.1 5899
-
 sulfite with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S Homo sapiens