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Literature summary extracted from

  • Wojdyla, Z.; Borowski, T.
    DFT study of the mechanism of manganese quercetin 2,3-dioxygenase quest for origins of enzyme unique nitroxygenase activity and regioselectivity (2016), J. Biol. Inorg. Chem., 21, 475-489 .
    View publication on PubMed

Metals/Ions

EC Number Metals/Ions Comment Organism Structure
1.13.11.24 Co2+ activates, Co-QDO Bacillus subtilis
1.13.11.24 Cu2+ activates, Cu-QDO, during the reaction mechanism of Cu-QDO dioxygen binds to the metal ion of the Cu-QDO-quercetin complex, yielding a Cu2+-superoxo quercetin radical intermediate, which then forms a Cu2+-alkylperoxo complex, the alkylperoxo complex evolves into endoperoxide intermediate that decomposes to the product Bacillus subtilis
1.13.11.24 Fe2+ activates, Fe-QDO Bacillus subtilis
1.13.11.24 Mn2+ activates, Mn-QDO, Mn2+ i the preferred metal ion. Mn-QDO in absence of O2 shows ability to react with nitroxyl (HNO)-singly reduced form of NO. HNO is incorporated into quercetin in the same manner as dioxygen, yet the reaction is strictly regioselective, as the only product is 2-((3,4-dihydroxyphenyl)(imino) methoxy)-4,6-dihydroxybenzoate Bacillus subtilis
1.13.11.24 additional information QDO is a mononuclear metalloenzyme hosting various transition metal ions (Cu2+, Mn2+, Fe2+) in its active site depending on the origin of the protein, different metal complex structures, overview Bacillus subtilis

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
1.13.11.24 quercetin + O2 Bacillus subtilis
-
 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
1.13.11.24 Bacillus subtilis
-
-
-

Reaction

EC Number Reaction Comment Organism Reaction ID
1.13.11.24 quercetin + O2 = 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+ the enzyme incorporates both atoms of dioxygen into the substrate by cleaving the central heterocycle ring and releasing CO. The enzyme activates quercetin through deprotonation and the proton acceptor-Glu69 needs to reorient for the reaction to proceed. Energy profiles and reaction schemes for nonenzymatic nitroxygenation of quercetin monoanion. Transient and intermediate structures, catalytic mechaanism, detailed overview Bacillus subtilis
a

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
1.13.11.24 additional information Mn-QDO in absence of O2 shows ability to react with nitroxyl (HNO)-singly reduced form of NO. HNO is incorporated into quercetin in the same manneras dioxygen, yet the reaction is strictly regioselective, as the only product is 2-((3,4-dihydroxyphenyl)(imino)methoxy)-4,6-dihydroxybenzoate Bacillus subtilis ?
-
 ?
1.13.11.24 quercetin + O2
-
 Bacillus subtilis 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
 ?

Synonyms

EC Number Synonyms Comment Organism
1.13.11.24 Co-QDO
-
 Bacillus subtilis
1.13.11.24 Fe-QDO
-
 Bacillus subtilis
1.13.11.24 manganese quercetin 2,3-dioxygenase
-
 Bacillus subtilis
1.13.11.24 Mn-QDO
-
 Bacillus subtilis
1.13.11.24 QDO
-
 Bacillus subtilis

General Information

EC Number General Information Comment Organism
1.13.11.24 additional information active site model, overview Bacillus subtilis
1.13.11.24 physiological function quercetin 2,3-dioxygenase (QDO) is an enzyme which accepts various transition metal ions as cofactors, and cleaves the heterocyclic ring of quercetin with consumption of dioxygen and release of carbon monoxide. QDO from Bacillus subtilis that binds Mn(II) displays an unprecedented nitroxygenase activity, whereby nitroxyl (HNO) is incorporated into quercetin cleavage products instead of dioxygen. The reaction proceeds with high regiospecificity, i.e. nitrogen and oxygen atoms of HNO are incorporated into specific fragments of the cleavage product. The reaction is an inherent property of the reactants, whereas the unique reactivity of Mn-QDO, as opposed to Co- or Fe-QDO that do not catalyze nitroxygenation. A nonenzymatic base-catalyzed reaction, which occurs in pH above 7.5, yields the same reaction products Bacillus subtilis