Violaxanthin de-epoxidase (VDE) (VDE)

Violaxanthin de-epoxidase (VDE) is a nuclear-encoded, thylakoid lumen-localized enzyme essential for the photoprotective xanthophyll cycle in plants and algae (UniProt P42520). It is a member of the lipocalin family and is activated when the thylakoid lumen becomes acidic (pH < 6.2) due to high light intensity (Jia et al., 2015, Plant Physiology). VDE catalyzes the conversion of the diepoxide violaxanthin to the epoxide-free zeaxanthin via the intermediate antheraxanthin. Zeaxanthin then interacts with light-harvesting complexes to trigger non-photochemical quenching (NPQ), which safely dissipates excess excitation energy as heat, preventing the formation of singlet oxygen and subsequent photo-oxidative damage (Müller et al., 2001, Plant Physiology). While VDE is not a target for human medicine, it is a primary target in agricultural biotechnology; for instance, accelerating the recovery of NPQ by overexpressing VDE alongside other proteins has been shown to increase crop biomass and yield in fluctuating light conditions (Kromdijk et al., 2016, Science). The enzyme is specifically inhibited by reducing agents such as dithiothreitol (DTT), which prevents the formation of essential disulfide bonds required for its activity (Yamamoto and Kamite, 1972, Biochimica et Biophysica Acta).

Other names

VDEVDE1Violaxanthin-antheraxanthin de-epoxidaseChloroplastic violaxanthin de-epoxidase

Catalyzes the de-epoxidation of violaxanthin to zeaxanthin via antheraxanthin in response to low lumenal pH; inhibited by reducing agents that disrupt disulfide bonds.