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EC 1.10.99.3 Details
EC number
1.10.99.3
Accepted name
violaxanthin de-epoxidase
Reaction
violaxanthin + 2 L-ascorbate = zeaxanthin + 2 L-dehydroascorbate + 2 H2O (overall reaction);;(1a) violaxanthin + L-ascorbate = antheraxanthin + L-dehydroascorbate + H2O;;(1b) antheraxanthin + L-ascorbate = zeaxanthin + L-dehydroascorbate + H2O
Other name(s)
VDE
Systematic name
violaxanthin:ascorbate oxidoreductase
CAS registry number
57534-73-3
Comment
Along with EC 1.14.13.90, zeaxanthin epoxidase, this enzyme forms part of the xanthophyll (or violaxanthin) cycle for controlling the concentration of zeaxanthin in chloroplasts. It is activated by a low pH of the thylakoid lumen (produced by high light intensity). Zeaxanthin induces the dissipation of excitation energy in the chlorophyll of the light-harvesting protein complex of photosystem II. In higher plants the enzyme reacts with all-trans-diepoxides, such as violaxanthin, and all-trans-monoepoxides, but in the alga Mantoniella squamata, only the diepoxides are good substrates.
History
created 2005, deleted 2014
EC Tree
1.12.1.1 created 1965, deleted 1972