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Information on EC 1.8.3.1 - sulfite oxidase and Organism(s) Homo sapiens and UniProt Accession P07850
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1.8.3.1 sulfite oxidaseIUBMB Comments
A molybdohemoprotein.
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Word Map
- 1.8.3.1
- molybdenum
- sulfur
- xanthine
- heme
- thiosulfate
- moco
- epr
- seizures
- molybdopterin
-
molybdoenzymes
-
sulfur-containing
- tungsten
-
molybdenum-containing
- pterin
- s-sulfocysteine
- soxs
- sulfurtransferase
-
ectopia
-
low-ph
-
pyranopterins
- lentis
-
dithiolene
-
amidoxime
-
eseem
-
hyperfine
- food industry
- agriculture
-
high-ph
- analysis
-
oxidase-deficient
- medicine
-
xanthinuria
-
marc
- molecular biology
- encephalomalacia
The taxonomic range for the selected organisms is: Homo sapiens
The enzyme appears in selected viruses and cellular organisms
The enzyme appears in selected viruses and cellular organisms
Synonyms
sulfite oxidase, shopper, atsox, sulfite:acceptor oxidoreductase, at-so, yedyz, sulfite oxidase homologue, sulfite acceptor oxidoreductase, 
more
topSYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
oxidase, sulfite
-
-
-
-
sulphite oxidase cytochrome b9
-
-
-
-
SUOX
REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
sulfite + O2 + H2O = sulfate + H2O2
catalytic cycle and electron transfer steps, and proposed oxidation state changes occurring at the Mo and Fe centers of one subunit of human sulfite oxidase during the catalytic oxidation of sulfite and the concomitant reduction of (cyt c)ox, overview
sulfite + O2 + H2O = sulfate + H2O2
electrocatalytic mechanism of HSO, overview
sulfite + O2 + H2O = sulfate + H2O2
quantum-mechanical study/quantum-mechanical cluster calculations of the reaction mechanism of sulfite oxidase using protonated and deprotonated substrates. The lowest barriers are obtained for a mechanism where the substrate attacks a Mo-bound oxo ligand, directly forming a Mo-bound sulfate complex, which then dissociates into the products. The activation energy is dominated by the Coulomb repulsion between the Mo complex and the substrate. The general catalytic cycle for sulfite oxidase includes the molybdenum ion refering to the molybdenum cofactor, and the iron ion refering to the heme, at the start of the catalytic cycle, Mo is in the oxidized +VI state and the heme group is in the Fe(III) state. Then SO3- binds and is oxidized to SO42-, while the Mo ion is reduced to the +IV state. To complete the catalytic cycle, the reduced Mo ion binds water and is reoxidized to the +VI state in two coupled one-electron/proton-transfer steps, proceeding via a transient Mo(V)-OH-state to form the active Mo(VI)=O form of the cofactor. The electrons are transferred via reduction of the heme, which subsequently is reoxidized by cytochrome c. Molecular mechanism of the oxo-atom transfer, modeling, detailed overview
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
redox reaction
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-
-
-
PATHWAY SOURCE
PATHWAYS
BRENDA
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-, -
SYSTEMATIC NAME
IUBMB Comments
sulfite:oxygen oxidoreductase
A molybdohemoprotein.
CAS REGISTRY NUMBER
COMMENTARY
9029-38-3
-
SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
nitrite + ferricytochrome c
nitric oxide + ferrocytochrome c
-
the enzyme can oxidize sulfite, and direct the electrons to reducing nitrite, to yield nitric oxide in the mitochondria
-
-
?
nitrite + H2O + porcine ferricytochrome c
nitric oxide + porcine ferrocytochrome c
the nitrite reduction mechanism involves sulfite oxidation, sulfate release and nitrite coordination at molybdenum with protonation-dependent nitric oxide and molybdenum V release. The highest nitric oxide production occurs between 0.01 and 0.0375 mM sulfite, with a dose-dependent inhibition of nitric oxide formation at higher sulfite concentrations
-
-
?
sulfite + H2O + porcine ferricyanide
sulfate + porcine ferrocyanide
-
-
-
?
sulfite + H2O + porcine ferricytochrome c
sulfate + porcine ferrocytochrome c
-
-
-
?
sulfite + cytochrome c
sulfate + reduced cytochrome c
-
-
-
-
?
sulfite + cytochrome c
sulfate + reduced cytochrome c
-
genetic deficiency results in neurological abnormities
-
-
?
sulfite + H2O + A
sulfate + AH2
-
the active site of the native enzyme can adopt both six-coordinate and five-coordinate geometries, which may be important in the catalytic mechanism, which may involve the binding of anions such as sulfite directly to Mo
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
-
lack of active enzyme produces severe neurodegeneration and early death in humans
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
sulfite is the physiological substrate
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
-
the enzyme catalyzes the oxidation of sulfite to sulfate using ferricytochrome c as the physiological electron acceptor
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
under normal physiological conditions, SO catalyzes the oxidation of sulfite to sulfate with cytochrome c (cyt c) as oxidizing substrate
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
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
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
usage of Fe3+ oxidized cytochrome c from horse heart
-
-
?
additional information
?
-
mechanism of oxidation of sulfite and radical generation by ferric cytochrome c (Fe3+ cyt c) in the absence and presence of H2O2, oxidation of sulfite by the Fe3+ cyt c increased with sulfite concentration, overview
-
-
?
additional information
?
-
-
mechanism of oxidation of sulfite and radical generation by ferric cytochrome c (Fe3+ cyt c) in the absence and presence of H2O2, oxidation of sulfite by the Fe3+ cyt c increased with sulfite concentration, overview
-
-
?
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
-
-
?
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
-
-
?
additional information
?
-
regeneration of the enzyme includes two, one-electron intramolecular electron transfers (IET) from the molybdenum (Mo) to the heme Fe and two, one-electron intermolecular electron transfers from the Fe to external ferricytochrome c
-
-
?
additional information
?
-
-
regeneration of the enzyme includes two, one-electron intramolecular electron transfers (IET) from the molybdenum (Mo) to the heme Fe and two, one-electron intermolecular electron transfers from the Fe to external ferricytochrome c
-
-
?
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
-
-
?
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
-
-
?
NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
sulfite + cytochrome c
sulfate + reduced cytochrome c
-
genetic deficiency results in neurological abnormities
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
-
lack of active enzyme produces severe neurodegeneration and early death in humans
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
sulfite is the physiological substrate
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
-
the enzyme catalyzes the oxidation of sulfite to sulfate using ferricytochrome c as the physiological electron acceptor
-
-
?
sulfite + O2 + H2O
sulfate + H2O2
under normal physiological conditions, SO catalyzes the oxidation of sulfite to sulfate with cytochrome c (cyt c) as oxidizing substrate
-
-
?
COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
cytochrome c
ferric cytochrome c, Fe3+ cyt c, cytochrome c is known to participate in mitochondrial respiration and has antioxidant and peroxidase activities. Fe3+ cyt c might have a role in the deleterious effects of sulfite in biological systems due to increased production of sulfite radical. Mammalian cytochrome c (cyt c) is a small, globular protein that exists in high concentrations in the inner membrane of mitochondria
heme
-
interactions of residue H90 with a heme propionate group destabilize the Fe(III) state of the heme
heme
the heme accepts electrons from the Mo ion following sulfite oxidation, a flexible connects the Mo and heme domains
molybdenum cofactor
the heme accepts electrons from the Mo ion following sulfite oxidation, a flexible connects the Mo and heme domains
molybdenum cofactor
the molybdenum cofactor (Moco) is bound in the active site of sulfite oxidase
molybdenum cofactor
three conserved residues (H304, R309, K322) are hydrogen bonded to the phosphate group of the molybdenum cofactor
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
-
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
-
additional information
vertebrate sulfite oxidases can use either cytochrome c or dioxygen as an electron acceptor
-
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Fe3+
Mo
Mo6+
Molybdenum
additional information
Mo
-
direct coordination of molybdenum by chloride. Increase in Mo-S/Cl ligation with reduced conditions of low-pH Cl- formation, relative to those of high-pH formation
Mo
-
the wild-type enzyme is five-coordinate with approximately square-based pyramidal geometry
Molybdenum
-
consists of a single molybdenum atom coordinated through the dithiolene group of a single molybdopterin molecule
Molybdenum
-
sulfite oxidation occurs at the dioxomolybdenum center of the enzyme
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
Molybdenum
in the catalytic reaction, SO is active in its fully oxidized state (MoVI) in which molybdenum is coordinated by a cysteine thiolate, the dithiolene group of molybdopterin, and two terminal oxygen atoms
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
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
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
nitrite
nitrite inhibits sulfite-dependent cytochrome c reduction at sulfite concentrations ranging from 0.01 to 0.1 mM
tungstate
-
treatment with sodium tungstate, leading to a catalytically inactive analogue by replacing molybdenum with tungsten in molybdenum cofactor because of its higher affinity constant. Determination of tolerance and impact of different concentrations of tungstate on the viability of HepG2 cells using a luciferase-based cytotoxicity assay, sodium tungstate is nontoxic up to 1000 ppm
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
additional information
-
electrocatalytic performance requires a sufficient SOx surface concentration in order to generate a catalytic current, and that the amount of cytochrome c within the assembly is high enough to provide a long-range electron transfer to connect the enzyme to the electrode
-
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.004
sulfite
with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme
0.0042
sulfite
with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme
0.0048
sulfite
with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S
0.0062
sulfite
with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S
0.0079
sulfite
with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
0.0082
sulfite
with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
0.0096
sulfite
with ferricanide, pH 6.0, 25°C, recombinant mutant C242S/C253S/C260S/C451S
0.0107
sulfite
with ferricanide, pH 8.4, 25°C, recombinant mutant C242S/C253S/C260S/C451S
0.0121
sulfite
with ferricanide, pH 6.0, 25°C, recombinant wild-type enzyme
0.0146
sulfite
with ferricanide, pH 8.4, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
0.0166
sulfite
with ferricanide, pH 8.4, 25°C, recombinant wild-type enzyme
0.0174
sulfite
with ferricanide, pH 8.9, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
0.019
sulfite
with ferricanide, pH 6.0, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
0.0196
sulfite
with ferricanide, pH 8.9, 25°C, recombinant wild-type enzyme
0.0288
sulfite
with ferricanide, pH 8.9, 25°C, recombinant mutant C242S/C253S/C260S/C451S
additional information
additional information
kinetics of sulfite oxidase-dependent nitrite reduction, the catalyzes single-electron transfer is similar to Michaelis-Menten kinetics
-
additional information
additional information
-
kinetics of sulfite oxidase-dependent nitrite reduction, the catalyzes single-electron transfer is similar to Michaelis-Menten kinetics
-
additional information
additional information
Michaelis-Menten steady-state kinetics of wild-type and mutant enzymes. All of the mutants show decreased rates of intramolecular electron transfer (IET) but increased steady-state rates of catalysis
-
additional information
additional information
-
Michaelis-Menten steady-state kinetics of wild-type and mutant enzymes. All of the mutants show decreased rates of intramolecular electron transfer (IET) but increased steady-state rates of catalysis
-
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
9.4
sulfite
with ferricanide, pH 6.0, 25°C, recombinant mutant C242S/C253S/C260S/C451S
13.9
sulfite
with ferricanide, pH 6.0, 25°C, recombinant wild-type enzyme
16.2
sulfite
with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme
19.8
sulfite
with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S
20.8
sulfite
with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme
25.8
sulfite
with ferricanide, pH 8.4, 25°C, recombinant mutant C242S/C253S/C260S/C451S
26.1
sulfite
with ferricanide, pH 6.0, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
27.3
sulfite
with ferricanide, pH 8.9, 25°C, recombinant wild-type enzyme
31.8
sulfite
with ferricanide, pH 8.9, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
32.4
sulfite
with ferricanide, pH 8.4, 25°C, recombinant wild-type enzyme
36.2
sulfite
with ferricanide, pH 8.9, 25°C, recombinant mutant C242S/C253S/C260S/C451S
37.7
sulfite
with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
41.2
sulfite
with ferricanide, pH 8.4, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
46.6
sulfite
with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
979
sulfite
with ferricanide, pH 6.0, 25°C, recombinant mutant C242S/C253S/C260S/C451S
1139
sulfite
with ferricanide, pH 6.0, 25°C, recombinant wild-type enzyme
1257
sulfite
with ferricanide, pH 8.9, 25°C, recombinant mutant C242S/C253S/C260S/C451S
1374
sulfite
with ferricanide, pH 6.0, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
1615
sulfite
with ferricanide, pH 8.9, 25°C, recombinant wild-type enzyme
1828
sulfite
with ferricanide, pH 8.9, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
1952
sulfite
with ferricanide, pH 8.4, 25°C, recombinant wild-type enzyme
2411
sulfite
with ferricanide, pH 8.4, 25°C, recombinant mutant C242S/C253S/C260S/C451S
2822
sulfite
with ferricanide, pH 8.4, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
3194
sulfite
with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S
4050
sulfite
with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme
4125
sulfite
with ferricanide, pH 7.1, 25°C, recombinant mutant C242S/C253S/C260S/C451S
4598
sulfite
with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
4952
sulfite
with ferricanide, pH 7.1, 25°C, recombinant wild-type enzyme
5899
sulfite
with ferricanide, pH 7.1, 25°C, recombinant selenomethionine-labeled mutant C242S/C253S/C260S/C451S
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
pH RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
6 - 11
pH dependence of the maximum catalytic oxidation current at the GC/HSO electrode with 4 mM sulfite and in the presence of 10 mM [Fe(tacn)]23+ in 100 mM mixed buffer solution, overview
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
25
pI VALUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE
-
expression in all brain regions examined: cerebellum, cerebral cortex, medulla, spinal cord, ocipital pole, frontal lobe, amygdala, caudate nucleus, corpus callosum, hippocampus, thalamus, temporal lobe, putamen. The cerebral cortex shows the highest level of expression
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
malfunction
physiological function
additional information
malfunction
-
defects in the enzyme cause a severe infant disease leading to early death with no efficient or costeffective therapy in sight
malfunction
in humans, sulfite oxidase deficiency is one of the most accepted causes of sulfite hypersensitivity and toxicity. A congenital deficiency of sulfite oxidase can cause an excessive accumulation of sulfite and lead to early death in infancy (usually between 2 and 6 years of age), or in neonatal cases, neurological abnormalities, mental retardation, intractable seizures, and ocular lens dislocation. Molybdenum cofactor deficiency, which compromises sulfite oxidase activity, results in profound mental retardation, brain damage, microcephaly, and spasticity. It has also been suggested that hypoxic-ischemic encephalopathy is due to molybdenum cofactor deficiency
malfunction
R309H and K322R mutations are responsible for isolated sulfite oxidase deficiency
physiological function
sulfite is detoxified in the liver and lung to sulfate by sulfite oxidase (SO), a molybdenum dependent mitochondrial enzyme. The enzyme ensures that intracellular levels of the sulfite ion remain at acceptably low levels. Sulfite oxidation is the final step in the metabolism of sulfur derived from sulfur containing amino acids. SO catalyzes the oxidation of endogenous or exogenous sulfite to sulfate, which is excreted in to the urine
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
physiological function
sulfite oxidase detoxifies sulfite by oxidizing it to sulfate, which detoxifies sulfite by oxidizing it to sulfate. This reaction is the terminal step in the biological sulfur cycle in many organisms, including humans
physiological function
-
sulfite oxidase is a mitochondria-located molybdenum-containing enzyme catalyzing the oxidation of sulfite to sulfate in the amino acid and lipid metabolism. It plays a major role in detoxification processes. It catalyzes the oxidation of sulfite to sulfate using ferricytochrome c as the physiological electron acceptor. This reaction is biologically essential as the final step in the catabolism of sulfur-containing amino acids cysteine and methionine. SuOx functions in detoxifying exogenously supplied sulfite and sulfur dioxide (e.g., pollution, preservatives)
physiological function
sulfite oxidase significantly contributes to hypoxic nitrite signaling as demonstrated by activation of the canonical NO-sGCcGMP pathway
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
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
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
52000
53500
-
1 * 53500, mutant G473D, gel filtration and sedimentation equilibrium analysis
66600
-
1 * 66600, double mutant R212A/G473D, sedimentation equilibrium analysis
SUBUNIT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
dimer
homodimer
monomer
monomer
-
1 * 53500, mutant G473D, gel filtration and sedimentation equilibrium analysis
monomer
-
1 * 66600, double mutant R212A/G473D, sedimentation equilibrium analysis
CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
vapor diffusion method, crystal structure of cytochrome b5 doamin at 1.2 A resolution
-
PROTEIN VARIANTS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
A208D
C242S/C253S/C260S/C451S
site-directed mutagenesis, mutation of the four active site Cys residues
D342K
-
significant decrease in the intramolecular electron transfer rate constant, kcat value is higher than the corresponding intramolecular electron transfer rate constant values, and the redox potentials of both metal centers are affected
F57A
-
the size and hydrophobicity of F57 play an important role in modulating the heme potential, residue F57 also affects the intramolecular electron transfer rate
F57Y
-
the size and hydrophobicity of F57 play an important role in modulating the heme potential, residue F57 also affects the intramolecular electron transfer rate
F79A
-
the size and hydrophobicity of F57 play an important role in modulating the heme potential, residue F57 also affects the intramolecular electron transfer rate
G473A
G473D
G473W
H304A R309H
site-directed mutagenesis, a mutation that removes the charge, hydrogen bonding, and is of smaller size, shows a decrease in Ksulfite m , thus binding sulfite more efficiently than the wild-type, kcat is increased compared to wild-type
H304R/R309H
site-directed mutagenesis, the mutant shows altered kinetics and reaction rates compared to the wild-type enzyme
H61Y/R160G
the mutations are associated with isolated sulfite oxidase deficiency
H90F
-
interactions of H90 with a heme propionate group destabilize the Fe(III) state of the heme
H90Y
-
interactions of H90 with a heme propionate group destabilize the Fe(III) state of the heme
K322R
site-directed mutagenesis, the mutant shows altered kinetics and reaction rates compared to the wild-type enzyme
R160K
-
the intramolecular electron transfer rate constant for the mutant enzyme is about one-fourth that of the wild-type enzyme
R160Q
R212A/G473D
-
mutant is able to oligomerize but has undetectable activity, significant random-coil formation
R309E
site-directed mutagenesis, the mutant shows altered kinetics and reaction rates compared to the wild-type enzyme, mutant R309E, which shows the greatest increase in activity, also shows the greatest increase in Km
R309H
site-directed mutagenesis, the mutant shows altered kinetics and reaction rates compared to the wild-type enzyme, purified R309H mutant enzyme has substantially increased catalytic activity and a slightly less efficient Km sulfite compared to the wild-type enzyme
R472D
-
significant decrease in the intramolecular electron transfer rate constant, and the redox potentials of both metal centers are affected
R472D/D342K
-
mutation reverses the charges of the salt bridge components, large decrease in intramolecular electron transfer rate constant
R472M
R472Q
Y343F
Y343X
-
isolated sulfite oxidase deficiency, shows early neonatal leukoencephalopathy and extensive symmetric cerebral injury especially white matter and basal ganglia
Y83A
-
mutation is located on the surface of the heme domain, but not in direct contact with the heme or the propionate groups, little effect on either intramolecular electron transfer or the heme potential
Y83F
-
mutation is located on the surface of the heme domain, but not in direct contact with the heme or the propionate groups, little effect on either intramolecular electron transfer or the heme potential
additional information
A208D
-
the intramolecular electron transfer rate constants at pH 6.0 are decreased by 3 orders of magnitude relative to that of the wild type, the active site structure of the Mo(V) form of A208D is different from that of the wild type
G473A
-
mutant is able to dimerize and has steady-state activity comparable to that of the wild type, stopped-flow analysis of the reductive half-reaction of this variant yields a rate constant nearly 3 times higher than that of the wild type
G473D
-
monomer, mutant is severely impaired both in the ability to bind sulfite and in catalysis, with a second-order rate constant 5 orders of magnitude lower than that of the wild type, significant random-coil formation
G473D
-
monomer, the Mo(V) active site structure is similar to that of the wild type, and the IET rate constant is only 2.6fold smaller than that of the wild type
G473W
-
monomer, mutant with 5fold higher activity than G473D and nearly wild-type activity at pH 7.0 when ferricyanide is the electron acceptor, significant random-coil formation
R160Q
-
the intramolecular electron transfer rate constant for the mutant enzyme at pH 6.0 is decreased by nearly 3 orders of magnitude relative to wild-type enzyme. The intramolecular electron transfer is rate-limiting in the catalytic cycle of the mutant, fatal impact of this mutation in patients with this genetic disorder
R160Q
-
at least three different Mo(V) species of R160Q exist as a function of pH (low pH type 1 and type 2, and high-pH). Mo(V) species with a blocked form of sulfite oxidase, with sulfate coordinated to the Mo center is the only species at pH higher or equal as 6 and remains a significant form at physiological pH, is six-coordinate and has a nearby exchangeable proton that is likely to be hydrogen-bonded to an oxygen of the sulfate ligand. The blocked structure of R160Q represents a catalytic dead end that contributes to the lethality of this mutant under physiological conditions
R160Q
-
clinical mutant, has a six-coordinate pseudooctahedral active site with coordination of glutamine Oepsilon to molybdenum
R160Q
-
mutation increases the Km for sulfite and decreases the kcat, resulting in a 1000fold decrease in catalytic efficiency. Reveals an increase in coordination number for the Mo, from 5 to 6
R472M
-
introduction of predicted catalytic site residues of assimilatory nitrate reductase, kinetic analysis
R472M
-
significant decrease in the intramolecular electron transfer rate constant, kcat value is higher than the corresponding intramolecular electron transfer rate constant values, and the redox potentials of both metal centers are affected
R472Q
-
introduction of predicted catalytic site residues of assimilatory nitrate reductase, kinetic analysis
R472Q
-
significant decrease in the intramolecular electron transfer rate constant, kcat value is higher than the corresponding intramolecular electron transfer rate constant values, and the redox potentials of both metal centers are affected
Y343F
-
in the mutant enzyme using cytochrome c as electron acceptor, turnover number is somewhat impaired, 34% of the wild-type activity at pH 8.5. The KM-value for the mutant enzyme shows a 5fold increase over wild-type. Reduction of the molybdenum center of the Y343 F variant by sulfite is more significantly impaired at high pH than at low pH
Y343F
-
increase in the Km-value for sulfite and a decrease in turnover number results in a 23fold attenuation in the specificity constant turnover (ratio of number to KM-value for sulfite) at optimum pH value of 8.25
Y343F
-
under low pH conditions the active site of Y343F is in the blocked form, with the Mo(V) center coordinated by sulfate. The Y343F mutation increases the apparent pKa of the transition from the low pH to high pH forms by ca. 2 pH units. An additional low pH form that has no exchangeable protons
additional information
-
optimized expression in Escherichia coli, untagged and His-tagged enzyme, expression in presence of tungstate
additional information
isolated sulfite oxidase deficiency, extensive brain damage in the gray matter and more pronounced damage in the white matter, without subsequent recovery. Early onset of energetic and metabolic imbalance. Impaired energetic status and accumulated metabolites
additional information
-
isolated sulfite oxidase deficiency, extensive brain damage in the gray matter and more pronounced damage in the white matter, without subsequent recovery. Early onset of energetic and metabolic imbalance. Impaired energetic status and accumulated metabolites
additional information
-
SUOX deficiency is typically inherited as a recessive autosomal trait for which there is no known therapy and typically results in death in infancy
additional information
all of the mutants show decreased rates of intramolecular electron transfer (IET) but increased steady-state rates of catalysis, IET is not the rate determining step for any of the mutations. Redox potentials of wild-tyype and mutant enzymes, overview
additional information
-
all of the mutants show decreased rates of intramolecular electron transfer (IET) but increased steady-state rates of catalysis, IET is not the rate determining step for any of the mutations. Redox potentials of wild-tyype and mutant enzymes, overview
additional information
-
construction of surface functionalized MoO3 nanoparticles that exhibit an intrinsic biomimetic SuOx activity that allows intracellular oxidation of sulfite to sulfate. Functionalized with a customized bifunctional ligand containing dopamine as anchor group and triphenylphosphonium ion as targeting agent, they selectively target the mitochondria while being highly dispersible in aqueous solutions. Chemically induced sulfite oxidase knockdown cells treated with MoO3 nanoparticles recover their sulfite oxidase activity in vitro, which makes MoO3 nanoparticles a potential therapeutic for sulfite oxidase deficiency and opens new avenues for cost-effective therapies for gene-induced deficiencies. Molybdenum trioxide (MoO3) is a well-known model compound for selective oxidation catalysis. Given their small size and surface-targeting moiety triphenylphosphonium ion (TPP), functionalized MoO3-TPP nanoparticles can cross the cellular membrane and accumulate specifically at the mitochondria, allowing recovery of the SuOx activity of tungstate knockdown human HepG2 hepatoblastoma cells. Steady-state kinetics of MoO3-TPP nanoparticles, a 4fold activity difference between nanoscale and bulkMoO3 indicates the importance of a higher surface area for attaining higher catalytic efficiencies
additional information
mediated electrocatalytic voltammetry of human sulfite oxidase (HSO) is demonstrated with synthetic one electron transfer iron complexes bis(1,4,7-triazacyclononane)iron(III) ([Fe(tacn)2]3+) and 1,2-bis(1,4,7-triaza-1-cyclononyl)ethane iron(III) ([Fe(dtne)]3+) at a glassy carbon working electrode, enzyme-dependent kinetics, overview. The HSO coupled electrode is successfully used for the determination of sulfite concentration in white wine and beer samples, and the results validate with a standard spectrophotometric method
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)
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)
PURIFICATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
phenyl-Sepharose column chromatography and Superdex 200 16/60 FPLC column gel filtration
-
CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
His-tagged SO expressed in Escherichia coli TP1000 cells containing plasmid pTG718
-
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
RENATURED/Commentary
ORGANISM
UNIPROT
LITERATURE
in vitro insertion of molybdopterin into aposulfite oxidase and conversion of molybdopterin into molybdenum cofactor
-
APPLICATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
analysis
an enzyme-coupled electrode is successfully used for the determination of sulfite concentration in white wine and beer samples, enzyme electrode preparation and method evaluation
food industry
-
artificial ETC composed of cytochrome c and sulfite oxidase formed by the layer-by-layer technique using a polyelectrolyte. The multilayer technology, e.g. sulfite oxidase-cyt c multilayer electrode may act as an anode in a bio-fuel cell and furthermore such multilayers may be exploited as a biosensor for the detection of sulfite, which is used as a preservative in wine and other foodstuffs
medicine
molecular biology
-
molybdenum trioxide (MoO3) nanoparticles display an intrinsic biomimetic sulfite oxidase activity under physiological conditions, and, functionalized with a customized bifunctional ligand containing dopamine as anchor group and triphenylphosphonium ion as targeting agent, they selectively target the mitochondria while being highly dispersible in aqueous solutions. Chemically induced sulfite oxidase knockdown cells treated with MoO3 nanoparticles recover their sulfite oxidase activity in vitro, which makes MoO3 nanoparticles a potential therapeutic for sulfite oxidase deficiency and opens new avenues for cost-effective therapies for gene-induced deficiencies. Molybdenum trioxide (MoO3) is a well-known model compound for selective oxidation catalysis
additional information
-
layer-by-layer assembly of globular proteins is feasible without use of polymers as counterpolyelectrolyte, which is interesting for the construction of third-generation biosensors. The assembly is made by co-adsorption of the enzyme SOx and the electron transfer protein cytochrome c
medicine
-
deficiency in SO, due to either a defect in molybdopterin cofactor biosynthesis or a mutation in the apo-enzyme gene itself, leads to dramatic neurological problems that can cause death in early infancy
medicine
-
low plasma total homocysteine is a valuable early indicator of sulfite oxidase dysfunction, providing a crucial first-line screen, whereas plasma cystine is not always informative in the first few days of life
medicine
magnetic resonance imaging and magnetic resonance spectroscopy measurements may help differentiate isolated sulfite oxidase deficiency from hypoxic-ischemic condition in patients in whom this diagnosis is not clinically suspected and may lead to further genetic antenatal inquiry that may prevent the birth of other infants affected with this severe and incurable congenital disease
medicine
-
molybdenum trioxide (MoO3) nanoparticles display an intrinsic biomimetic sulfite oxidase activity under physiological conditions, and, functionalized with a customized bifunctional ligand containing dopamine as anchor group and triphenylphosphonium ion as targeting agent, they selectively target the mitochondria while being highly dispersible in aqueous solutions. Chemically induced sulfite oxidase knockdown cells treated with MoO3 nanoparticles recover their sulfite oxidase activity in vitro, which makes MoO3 nanoparticles a potential therapeutic for sulfite oxidase deficiency and opens new avenues for cost-effective therapies for gene-induced deficiencies. Molybdenum trioxide (MoO3) is a well-known model compound for selective oxidation catalysis
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JOURNAL
VOL.
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ORGANISM (UNIPROT)
PUBMED ID
SOURCE
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Homo sapiens
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Homo sapiens
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305
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Biochemistry
42
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2003
Homo sapiens
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Role of conserved tyrosine 343 in intramolecular electron transfer in human sulfite oxidase
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278
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Homo sapiens
Wilson, H.L.; Rajagopalan, K.V.
The role of tyrosine 343 in substrate binding and catalysis by human sulfite oxidase
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279
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2004
Homo sapiens
Feng, C.; Wilson, H.L.; Tollin, G.; Astashkin, A.V.; Hazzard, J.T.; Rajagopalan, K.V.; Enemark, J.H.
The pathogenic human sulfite oxidase mutants G473D and A208D are defective in intramolecular electron transfer
Biochemistry
44
13734-13743
2005
Homo sapiens
Wilson, H.L.; Wilkinson, S.R.; Rajagopalan, K.V.
The G473D mutation impairs dimerization and catalysis in human sulfite oxidase
Biochemistry
45
2149-2160
2006
Homo sapiens
Harris, H.H.; George, G.N.; Rajagopalan, K.V.
High-resolution EXAFS of the active site of human sulfite oxidase: comparison with density functional theory and X-ray crystallographic results
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45
493-495
2006
Homo sapiens
Astashkin, A.V.; Feng, C.; Raitsimring, A.M.; Enemark, J.H.
17O ESEEM Evidence for Exchange of the Axial Oxo Ligand in the Molybdenum Center of the High pH Form of Sulfite Oxidase
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127
502-503
2005
Homo sapiens
Doonan, C.J.; Wilson, H.L.; Bennett, B.; Prince, R.C.; Rajagopalan, K.V.; George, G.N.
MoV electron paramagnetic resonance of sulfite oxidase revisited: the low-pH chloride signal
Inorg. Chem.
47
2033-2038
2008
Homo sapiens
Raitsimring, A.M.; Astashkin, A.V.; Feng, C.; Wilson, H.L.; Rajagopalan, K.V.; Enemark, J.H.
Studies of the Mo(V) center of the Y343F mutant of human sulfite oxidase by variable frequency pulsed EPR spectroscopy
Inorg. Chim. Acta
361
941-946
2008
Homo sapiens
Doonan, C.J.; Wilson, H.L.; Rajagopalan, K.V.; Garrett, R.M.; Bennett, B.; Prince, R.C.; George, G.N.
Modified active site coordination in a clinical mutant of sulfite oxidase
J. Am. Chem. Soc.
129
9421-9428
2007
Homo sapiens
Dronov, R.; Kurth, D.G.; Moehwald, H.; Spricigo, R.; Leimkuehler, S.; Wollenberger, U.; Rajagopalan, K.V.; Scheller, F.W.; Lisdat, F.
Layer-by-layer arrangement by protein-protein interaction of sulfite oxidase and cytochrome c catalyzing oxidation of sulfite
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130
1122-1123
2008
Homo sapiens
Astashkin, A.V.; Johnson-Winters, K.; Klein, E.L.; Feng, C.; Wilson, H.L.; Rajagopalan, K.V.; Raitsimring, A.M.; Enemark, J.H.
Structural studies of the molybdenum center of the pathogenic R160Q mutant of human sulfite oxidase by pulsed EPR spectroscopy and 17O and 33S labeling
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130
8471-8480
2008
Homo sapiens
Hoffmann, C.; Ben-Zeev, B.; Anikster, Y.; Nissenkorn, A.; Brand, N.; Kuint, J.; Kushnir, T.
Magnetic resonance imaging and magnetic resonance spectroscopy in isolated sulfite oxidase deficiency
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22
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2007
Homo sapiens (P51687), Homo sapiens
Workun, G.J.; Moquin, K.; Rothery, R.A.; Weiner, J.H.
Evolutionary persistence of the molybdopyranopterin-containing sulfite oxidase protein fold
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72
228-48
2008
Arabidopsis thaliana (Q9S850), Bacillus licheniformis, Bacillus sp. (in: Bacteria), Bacillus sp. (in: Bacteria) NRRL B-14911, Chlorella vulgaris, Deinococcus radiodurans, Erythrobacter litoralis, Escherichia coli, Gallus gallus (P07850), Homo sapiens, Maribacter sp. HTCC2170, Ogataea angusta, Paenarthrobacter aurescens, Rhizorhabdus wittichii RW1 (A5V4U9), Roseovarius nubinhibens, Rubrobacter xylanophilus, Saccharopolyspora erythraea, Spinacia oleracea, Streptomyces ambofaciens, Thermus thermophilus, Zea mays
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Isolated sulfite oxidase deficiency in the newborn: lactic acidaemia and leukoencephalopathy
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38
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2007
Homo sapiens
Haensch, R.; Lang, C.; Rennenberg, H.; Mendel, R.R.
Significance of plant sulfite oxidase
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9
589-595
2007
Arabidopsis thaliana, Cytisus scoparius, Gallus gallus, Hedera helix, Homo sapiens, Nicotiana plumbaginifolia, Phragmites australis, Populus tremula x Populus alba, Quercus ilex, Rattus norvegicus, Spinacia oleracea
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Electrocatalytically functional multilayer assembly of sulfite oxidase and cytochrome c
Soft Matter
4
972-978
2008
Homo sapiens
Qiu, J.; Wilson, H.; Rajagopalan, K.
Structure-based alteration of substrate specificity and catalytic activity of sulfite oxidase from sulfite oxidation to nitrate reduction
Biochemistry
51
1134-1147
2012
Gallus gallus (P07850), Gallus gallus, Homo sapiens
Davis, A.; Cornelison, M.; Meyers, K.; Rajapakshe, A.; Berry, R.; Tollin, G.; Enemark, J.
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42
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2013
Homo sapiens
Johnson-Winters, K.; Davis, A.C.; Arnold, A.R.; Berry, R.E.; Tollin, G.; Enemark, J.H.
Probing the role of a conserved salt bridge in the intramolecular electron transfer kinetics of human sulfite oxidase
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18
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2013
Homo sapiens
Ragg, R.; Natalio, F.; Tahir, M.N.; Janssen, H.; Kashyap, A.; Strand, D.; Strand, S.; Tremel, W.
Molybdenum trioxide nanoparticles with intrinsic sulfite oxidase activity
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8
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2014
Homo sapiens
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.
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23
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Homo sapiens (P51687), Homo sapiens
Velayutham, M.; Hemann, C.F.; Cardounel, A.J.; Zweier, J.L.
Sulfite oxidase activity of cytochrome c role of hydrogen peroxide
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5
96-104
2016
Homo sapiens (P51687), Homo sapiens
Kalimuthu, P.; Belaidi, A.; Schwarz, G.; Bernhardt, P.
Low potential catalytic voltammetry of human sulfite oxidase
Electrochim. Acta
199
280-289
2016
Homo sapiens (P51687)
-
van Severen, M.C.; Andrejic, M.; Li, J.; Starke, K.; Mata, R.A.; Nordlander, E.; Ryde, U.
A quantum-mechanical study of the reaction mechanism of sulfite oxidase
J. Biol. Inorg. Chem.
19
1165-1179
2014
Homo sapiens (P51687)
Davis, A.C.; Johnson-Winters, K.; Arnold, A.R.; Tollin, G.; Enemark, J.H.
Kinetic results for mutations of conserved residues H304 and R309 of human sulfite oxidase point to mechanistic complexities
Metallomics
6
1664-1670
2014
Homo sapiens (P51687), Homo sapiens
Bender, D.; Tobias Kaczmarek, A.; Niks, D.; Hille, R.; Schwarz, G.
Mechanism of nitrite-dependent NO synthesis by human sulfite oxidase
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Homo sapiens (P51687), Homo sapiens
Mutus, B.
The catalytic mechanism for NO production by the mitochondrial enzyme, sulfite oxidase
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476
1955-1956
2019
Homo sapiens
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