Violaxanthin de epoxidase

Violaxanthin de-epoxidase (EC 1.10.99.3, VDE) is an enzyme with systematic name violaxanthin:ascorbate oxidoreductase. This enzyme catalyses the following chemical 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

Violaxanthin de-epoxidase is a part of the xanthophyll (or violaxanthin) cycle for controlling the concentration of zeaxanthin in chloroplasts.