The roles of specific xanthophylls in photoprotection
The xanthophyll cycle involves the enzymatic removal of epoxygroups from xanthophylls (e.g. , antheraxanthin,diadinoxanthin) to create so-called de-epoxidised xanthophylls(e.g. diatoxanthin, ). These enzymatic cycles werefound to play a key role in stimulating energy dissipation withinlight harvesting antenna proteins by - a mechanism to reduce the amount of energy thatreaches the photosynthetic reaction centers. is one of the main ways of protecting against . Inhigher plants there are three carotenoid pigments that are activein the xanthophyll cycle: , antheraxanthin andzeaxanthin. During light stress violaxanthin is converted tozeaxanthin via the intermediate antheraxanthin, which plays adirect photoprotective role acting as a lipid-protective and by stimulating within light harvesting proteins. This conversion of violaxanthinto zeaxanthin is done by the enzyme violaxanthin de-epoxidase,while the reverse reaction is performed by zeaxanthin epoxidase
03/10/1997 · A Role in NPQ for Xanthophylls ..
Xanthophylls: Oxygenated carotenoids. Important xanthophylls found in zooxanthellae are diadinoxanthin and diatoxanthin - these play an important role in protecting them from excessive light. Dinoxanthin is an accessory pigment that transfers collected energy to dinoflagellates photosystems (with an unknown efficiency) and might act as an antioxidant as well.
Xanthophylls (oxygenated carotenoids) are also found in zooxanthellae. Two xanthophylls (diadinoxanthin and diatoxanthin) play an important role in protecting symbiotic algae and coral hosts from excessive light energy. When light energy is sufficient enough to effect pH changes within the photosynthetic apparatus of zooxanthellae, diadinoxanthin is converted to diatoxanthin. This conversion shunts light energy away from photosynthesis. In darkness, the process reverses, and diatoxanthin becomes diadinoxanthin. Note that these xanthophylls both absorb some violet but most strongly blue wavelengths at ~450 - 490nm. See Figure 28.