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Literature summary for 1.8.3.1 extracted from

  • 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 (2014), J. Biol. Inorg. Chem., 19, 1165-1179 .
    View publication on PubMed
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Metals/Ions

Metals/Ions Comment Organism Structure
Fe3+
-
 Homo sapiens
Mo6+
-
 Homo sapiens

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
sulfite + O2 + H2O Homo sapiens
-
 sulfate + H2O2
-
 ?

Organism

Organism UniProt Comment Textmining
Homo sapiens P51687
-
-

Reaction

Reaction Comment Organism Reaction ID
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 Homo sapiens
a

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
sulfite + O2 + H2O
-
 Homo sapiens sulfate + H2O2
-
 ?

Cofactor

Cofactor Comment Organism Structure
cytochrome c
-
 Homo sapiens
heme
-
 Homo sapiens
molybdenum cofactor the molybdenum cofactor (Moco) is bound in the active site of sulfite oxidase Homo sapiens

General Information

General Information Comment Organism
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 Homo sapiens