Violaxanthin de-epoxidase, the xanthophyll cycle enzyme, requires lipid inverted hexagonal structures for its activity

Bilayer-forming lipids were shown to be ineffective in sustaining the enzymatic activity of violaxanthin de-epoxidase. On the other hand, non-bilayer-forming lipids, regard-less of their different chemical character, ensured high activity of violaxanthin de-epoxidase, resulting in conversion of violaxanthin to zeaxanthin. Our data indicates that the presence of lipids forming reversed hexagonal structures is necessary for violaxanthin de-epoxidase activity and this activity is dependent on the degree of unsaturation of the fatty acids. The significance of the reversed hexagonal phase domains in the conversion of violaxanthin into zeaxanthin in model systems and in the native thylakoid membranes is discussed.