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EC Number

Catalytic Site Atlas

CSA LITERATURE entry for 1gp5

E.C. nameleucocyanidin oxygenase
SpeciesArabidopsis thaliana (Thale cress)
E.C. Number (IntEnz)
CSA Homologues of 1gp5There are 54 Homologs
CSA Entries With UniProtID Q96323
CSA Entries With EC Number
PDBe Entry 1gp5
PDBSum Entry 1gp5
MACiE Entry 1gp5

Literature Report

IntroductionThe 2oxoglutarate dependent enzyme Anthocyanidin synthase is able to catalyse the synthesis of anthocyanidin from quercetin, a vital step in the synthesis of flavoids and flavones in plant cells. The reaction is coupled to the decarboxylation of 2-oxoglutarate to form succinate. It is part of the family of 2OG dependent non-haem iron oxygenases, which use 2oxoglutarate as a cosubstrate and Iron (II) as a cofactor in their reaction mechanisms. The enzyme is of particular interest to geneticists as a mutated form is responsible for the original tall/dwarf dimorphism observed in peas by Mendel.
MechansimIn the first stage of the reaction the iron (II) ion acts as a nucleophile to attack molecular oxygen, thus reducing it to a peroxide radical, and oxidising iron (II) to iron (III). The radical then reacts with the 2C of the 2 oxoglutarate to create an unstable intermediate which loses CO2 to give iron IV with a double bond formed to oxygen. The reduction of iron to Fe (III) then allows the double bond to break, so that the oxygen can strip a proton from the substrate quercetin to leave a radical. The radical then allows the OH to break its bond to the iron, forming iron (II) and an acetal. Deprotonation of the acetal by Lys 213 results in the return of the OH to the Iron (II), now acting as a Lewis acid, and forms the product Anthocyanidin.

Catalytic Sites for 1gp5

Annotated By Reference To The Literature - Site 2 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
LysA213213macie:sideChainDeprotonates quercetin to allow a double bond to form so that dehydration occurs resulting in the Anthrocyadin product.

Literature References

Wilmouth RC
Structure and mechanism of anthocyanidin synthase from Arabidopsis thaliana.
Structure 2002 10 93-103
PubMed: 11796114