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sulfite + O2 + H2O = sulfate + H2O2
sulfite + O2 + H2O = sulfate + H2O2
ping-pong mechanism
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sulfite + O2 + H2O = sulfate + H2O2
ping-pong mechanism
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sulfite + O2 + H2O = sulfate + H2O2
this direct reduction of O2 is prevented completely in presence of cytochrome c
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sulfite + O2 + H2O = sulfate + H2O2
x-ray absorption spectroscopy of oxidation states
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sulfite + O2 + H2O = sulfate + H2O2
intramolecular electron transfer and effect of solution viscosity
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sulfite + O2 + H2O = sulfate + H2O2
kinetics and proposed mechanism
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sulfite + O2 + H2O = sulfate + H2O2
mechanism and kinetics of electron transfer
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sulfite + O2 + H2O = sulfate + H2O2
mechanism and kinetics of electron transfer
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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
sulfite + O2 + H2O = sulfate + H2O2
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nitrite + ferricytochrome c
nitric oxide + ferrocytochrome c
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the enzyme can oxidize sulfite, and direct the electrons to reducing nitrite, to yield nitric oxide in the mitochondria
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?
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
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?
selenite + ferricyanide + H2O
? + ferrocyanide
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approximately 5% of the observed sulfite activity
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?
SO32- + H2O + 2 Fe(III)cytochrome c
SO42- + 2 Fe(II)cytochrome c + 2 H+
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?
SO32- + H2O + 2 ferricyanide
SO42- + 2 ferrocyanide + 2 H+
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?
SO32- + H2O + 2 ferricytochrome c
SO42- + 2 ferrocytochrome c + 2 H+
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?
SO32- + H2O + O2
SO42- + H2O2
sodium sulfite + H2O + A
NaSO42- + AH2
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
sulfite + ferricyanide + H+
sulfate + reduced ferricyanide
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
sulfite + H2O + A
SO42- + AH2
sulfite + H2O + A
sulfate + AH2
sulfite + H2O + ferricyanide
sulfate + ferrocyanide
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ir
sulfite + H2O + O2
sulfate + hydrogen peroxide
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?
sulfite + H2O + porcine ferricyanide
sulfate + porcine ferrocyanide
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?
sulfite + H2O + porcine ferricytochrome c
sulfate + porcine ferrocytochrome c
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?
sulfite + O2 + H2O
sulfate + H2O2
sulfite + O2 + H2O
sulfate + hydrogen peroxide
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?
additional information
?
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SO32- + H2O + O2
SO42- + H2O2
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?
SO32- + H2O + O2
SO42- + H2O2
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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significantly slower activity than that observed with ferricyanide
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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catalytic cycle
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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genetic deficiency results in neurological abnormities
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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detoxification
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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natural acceptor
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
substrates horse heart cytochrome c, and recombinant Starkeya novella cytochrome c are only reduced to about 40% while Sinorhizobium meliloti cytochrome c is almost completely reduced. Enzyme interacts with two small redox proteins, a cytochrome c and a Cu containing pseudoazurin, that are encoded in the same operon and are co-transcribed with the sorT gene
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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?
sulfite + cytochrome c
sulfate + reduced cytochrome c
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detoxification
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?
sulfite + ferricyanide + H+
sulfate + reduced ferricyanide
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?
sulfite + ferricyanide + H+
sulfate + reduced ferricyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + ferricyanide + H2O
sulfate + ferrocyanide
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?
sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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A: electron acceptor, i.e. O2, cytochrome c, K3[Fe(CN)6], 2,6-dichloroindophenol, methylene blue, highly specific for sulfite as electron donor
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?
sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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A: electron acceptor, i.e. O2, cytochrome c, K3[Fe(CN)6], 2,6-dichloroindophenol, methylene blue, highly specific for sulfite as electron donor
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?
sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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A: electron acceptor, i.e. O2, cytochrome c, K3[Fe(CN)6], 2,6-dichloroindophenol, methylene blue, highly specific for sulfite as electron donor
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sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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artificial A: tetramethylphenylenediamine, 2,6-dichloroindophenol, methylene blue
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?
sulfite + H2O + A
SO42- + AH2
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H2O2 acceptor only when respiratory chain is inhibited
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?
sulfite + H2O + A
SO42- + AH2
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A: electron acceptor, i.e. O2, cytochrome c, K3[Fe(CN)6], 2,6-dichloroindophenol, methylene blue, highly specific for sulfite as electron donor
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sulfite + H2O + A
SO42- + AH2
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sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
SO42- + AH2
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?
sulfite + H2O + A
sulfate + AH2
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?
sulfite + H2O + A
sulfate + AH2
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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
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sulfite + H2O + A
sulfate + AH2
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sulfite + H2O + A
sulfate + AH2
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?
sulfite + H2O + A
sulfate + AH2
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the initial step in the oxygen-atom transfer reaction with HSO3- takes place by oxoanionic binding of the substrate to the MoVI center with the formation of a stable Michaelis complex
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sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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lack of active enzyme produces severe neurodegeneration and early death in humans
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sulfite + O2 + H2O
sulfate + H2O2
sulfite is the physiological substrate
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?
sulfite + O2 + H2O
sulfate + H2O2
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the enzyme catalyzes the oxidation of sulfite to sulfate using ferricytochrome c as the physiological electron acceptor
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?
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
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?
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
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?
sulfite + O2 + H2O
sulfate + H2O2
usage of Fe3+ oxidized cytochrome c from horse heart
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?
sulfite + O2 + H2O
sulfate + H2O2
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r
sulfite + O2 + H2O
sulfate + H2O2
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r
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
sulfite + O2 + H2O
sulfate + H2O2
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?
additional information
?
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the enzyme is believed to detoxify excess sulfite that is produced during sulfur assimilation, or due to air pollution
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additional information
?
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the enzyme is believed to detoxify excess sulfite that is produced during sulfur assimilation, or due to air pollution
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additional information
?
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No activity is found with cytochrome c as electron acceptor, since the heme domain known to mediate electron transfer between the molybdenum cofactor-domain and cytochrome c in rat hepatic SO is missing in the plant enzyme
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additional information
?
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the enzyme does not react with cytochrome c
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additional information
?
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sulfite ligand docking study, arginine residues particularly Arg374 is crucial for SOX-sulfite binding and two other residues Arg51 and Arg103 are also implicated to be important for SOX-sulfite bindings in plants
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?
additional information
?
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sulfite ligand docking study, arginine residues particularly Arg374 is crucial for SOX-sulfite binding and two other residues Arg51 and Arg103 are also implicated to be important for SOX-sulfite bindings in plants
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additional information
?
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the plant sulfite oxidase does not accept cyctochrome c as substrate
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additional information
?
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sulfite ligand docking study
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additional information
?
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sulfite ligand docking study
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additional information
?
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the plant sulfite oxidase does not accept cyctochrome c as substrate
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?
additional information
?
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The optimal substrate or precise physiological role for YedYZ in Escherichia coli and its well-conserved orthologs in other bacteria remains unknown.
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?
additional information
?
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R138, R190, and R450 contribute to a positively charged binding pocket, which stabilizes substrate/product binding
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?
additional information
?
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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
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?
additional information
?
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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
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?
additional information
?
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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
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?
additional information
?
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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
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?
additional information
?
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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
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?
additional information
?
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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
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?
additional information
?
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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
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?
additional information
?
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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
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?
additional information
?
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sulfite ligand docking study
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?
additional information
?
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sulfite ligand docking study
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?
additional information
?
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the plant sulfite oxidase does not accept cyctochrome c as substrate
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?
additional information
?
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sulfite ligand docking study
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?
additional information
?
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sulfite ligand docking study
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?
additional information
?
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the plant sulfite oxidase does not accept cyctochrome c as substrate
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additional information
?
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Oax-Mo-Sthiolate-C dihedral angles near 90° effectively eliminate covalency contributions to the Mo(xy) redox orbital from the thiolate sulfur. The Oax-Mo-Sthiolate-C dihedral angle is shown to have a pronounced effect on the relative intensity ratios of the XAS spin-allowed S(1s)fSv(p) + Mo-(xy) and S(1s)fSv(p) + Mo(xz,yz) transitions
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?
additional information
?
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the plant sulfite oxidase does not accept cyctochrome c as substrate
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?
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1.8.3.1 sulfite oxidase
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