Kinetics of violaxanthin de-epoxidation by violaxanthin de-epoxidase, a xanthophyll cycle enzyme, is regulated by membrane fluidity in model lipid bilayers. Eur J Biochem

Department of Plant Physiology and Biochemistry, The Jan Zurzycki Institute of Molecular Biology and Biotechnology, Jagiellonian University, Kraków, Poland.
European Journal of Biochemistry (Impact Factor: 3.58). 10/2002; 269(18):4656-65. DOI: 10.1046/j.1432-1033.2002.03166.x
Source: PubMed


This paper describes violaxanthin de-epoxidation in model lipid bilayers. Unilamellar egg yolk phosphatidylcholine (PtdCho) vesicles supplemented with monogalactosyldiacylglycerol were found to be a suitable system for studying this reaction. Such a system resembles more the native thylakoid membrane and offers better possibilities for studying kinetics and factors controlling de-epoxidation of violaxanthin than a system composed only ofmonogalactosyldiacylglycerol and is commonly used in xanthophyll cycle studies. The activity of violaxanthin de-epoxidase (VDE) strongly depended on the ratio of monogalactosyldiacylglycerol to PtdCho in liposomes. The mathematical model of violaxanthin de-epoxidation was applied to calculate the probability of violaxanthin to zeaxanthin conversion at different phases of de-epoxidation reactions. Measurements of deepoxidation rate and EPR-spin label study at different temperatures revealed that dynamic properties of the membrane are important factors that might control conversion of violaxanthin to antheraxanthin. A model of the molecular mechanism of violaxanthin de-epoxidation where the reversed hexagonal structures (mainly created by monogalactosyldiacylglycerol) are assumed to be required for violaxanthin conversion to zeaxanthin is proposed. The presence of monogalactosyldiacylglycerol reversed hexagonal phase was detected in the PtdCho/monogalactosyldiacylglycerol liposomes membrane by 31P-NMR studies. The availability of violaxanthin for de-epoxidation is a diffusion-dependent process controlled by membrane fluidity. The significance of the presented results for understanding themechanism of violaxanthin de-epoxidation in native thylakoid membranes is discussed.

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Available from: Anna Kostecka-Gugala, Jan 07, 2016
    • "Role of MGDG in V de-epoxidation. The presence of the main thylakoid membrane lipid monogalactosyldiacylglycerole (MGDG) is essential for the efficient de-epoxidation of V to A and Z (Fig. 2, Latowski et al., 2002; Goss et al., 2005, 2007). The role of MGDG is twofold: first, it serves as solubilizing agent for the hydrophobic xanthophyll cycle pigment V, thus making the substrate accessible for the enzyme VDE (Goss et al., 2005). "
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    ABSTRACT: In their natural environment plants and algae are exposed to rapidly changing light conditions and light intensities. Illumination with high light intensities has the potential to overexcite the photosynthetic pigments and the electron transport chain and thus induce the production of toxic reactive oxygen species (ROS). To prevent damage by the action of ROS, plants and algae have developed a multitude of photoprotection mechanisms. One of the most important protection mechanisms is the dissipation of excessive excitation energy as heat in the light-harvesting complexes of the photosystems. This process requires a structural change of the photosynthetic antenna complexes that are normally optimized with regard to efficient light-harvesting. Enhanced heat dissipation in the antenna systems is accompanied by a strong quenching of the chlorophyll a fluorescence and has thus been termed non-photochemical quenching of chlorophyll a fluorescence, NPQ. The general importance of NPQ for the photoprotection of plants and algae is documented by its wide distribution in the plant kingdom. In the present review we will summarize the present day knowledge about NPQ in higher plants and different algal groups with a special focus on the molecular mechanisms that lead to the structural rearrangements of the antenna complexes and enhanced heat dissipation. We will present the newest models for NPQ in higher plants and diatoms and will compare the features of NPQ in different algae with those of NPQ in higher plants. In addition, we will briefly address evolutionary aspects of NPQ, i.e. how the requirements of NPQ have changed during the transition of plants from the aquatic habitat to the land environment. We will conclude with a presentation of open questions regarding the mechanistic basis of NPQ and suggestions for future experiments that may serve to obtain this missing information.
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    • "A high concentration of Dt in the thylakoid lipid phase is in line with increased photoprotection by Dt (Lepetit et al. 2010). Additionally, MGDG forms what are termed inverted hexagonal (H II ) phases essential for efficient de-epoxidation (Latowski et al. 2002; Goss et al. 2005, 2007). H II phases are likely associated with the FCP complexes and represent the docking sites for DDE once the enzyme has been activated by ΔpH (Lepetit et al. 2010, 2012), i.e. the MGDG shield around the LHC targets DDE to the site where the majority of Dd is located. "
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    ABSTRACT: Diatoms and brown algae are major contributors to marine primary production. They are biologically diverse, with thousands of different species, and are extremely successful, occupying almost every marine ecosystem ranging from the coastal-estuarine to deep-sea regions. Their ecological success is based in part on their ability to rapidly regulate photosynthesis in response to pronounced fluctuations in their natural light environment. Regulation of light harvesting, and the use of excitation energy, is largely based on effective dissipation of excessive energy as heat. Thermal dissipation of excitation energy is assessed as non-photochemical quenching of chlorophyll a fluorescence (NPQ). NPQ depends strongly on the conversion of xanthophylls: diadinoxanthin (Dd) to diatoxanthin (Dt) in the Dd-Dt cycle of diatoms and violaxanthin (V) to zeaxanthin (Z), via the intermediate antheraxanthin (A), in the VAZ cycle present in brown algae. Xanthophyll cycle (XC)-dependent thermal energy dissipation underlying NPQ represents one of the most important photoprotection mechanisms of diatoms and brown algae. In the present chapter, we review the biochemistry of XC enzymes with a special focus on co-substrate requirements and regulation of enzyme activity. In addition, we present a new model for the structural basis of XC-dependent NPQ in diatoms based on the latest experimental findings. In the last section, we highlight the importance of XC-dependent photoprotection for the ecological success of diatoms and brown algae in their natural environments.
    Full-text · Chapter · Oct 2014
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    • "De-epoxydation was stopped by mixing 700 ml of assay mixture with 50 ml of 1 M KOH (Yamamoto, 1985). The level of xanthophyll pigments (violaxanthin as a substrate, antheraxanthin and zeaxanthin as products) was analyzed by reverse phase HPLC chromatography (Latowski et al., 2002). "
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    ABSTRACT: In the diadinoxanthin cycle the epoxy group is removed from diadinoxanthin and diatoxanthin is created. This conversion takes place e.g. in diatoms with the involvement of the enzyme diadinoxanthin de-epoxidase. In one of the diatom species, Phaeodactylum tricornutum (CCAP 1055/1 strain with genome sequenced) three de-epoxidase genes (PtVDE, PtVDL1, PtVDL2) have been identified, but only one of them (PtVDE) corresponds to violaxanthin de-epoxidase, an enzyme which is commonly found in higher plants. In these studies, the expression of two de-epoxidase genes of another Phaeodactylum tricornutum strain (UTEX 646), which is commonly used in diatom studies, were obtained in Origami b and BL21 E. coli strains. The molecular masses of the mature proteins are about 49 kDa and 60 kDa, respectively, for VDE and VDL2. Both enzymes are active with violaxanthin as a substrate.
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