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Báo cáo khoa học: Kinetics of violaxanthin de-epoxidation by violaxanthin de-epoxidase, a xanthophyll cycle enzyme, is regulated by membrane fluidity in model lipid bilayers

This paper describes violaxanthin de-epoxidation in model lipid bilayers. Unilamellar egg yolk phosphatidylcholine (PtdCho) vesicles supplemented with monogalactosyldi-acylglycerol 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 systemcomposed only of monogalacto-syldiacylglycerol and is commonly used in xanthophyll cycle studies. . | Eur. J. Biochem. 269 4656-4665 2002 FEBS 2002 doi 10.1046 j.1432-1033.2002.03166.x Kinetics of violaxanthin de-epoxidation by violaxanthin de-epoxidase a xanthophyll cycle enzyme is regulated by membrane fluidity in model lipid bilayers Dariusz Latowski1 Jerzv Kruk1. Kvetoslava Burda2. Marta Skrzvnecka-Jaskier1 Anna Kostecka-Guaata1 w BV V 4 BB V V w B V B BB w w B w w B B w BV w B BB BB Bl w B B BB IV BB BV B w B B BWBBBB BB B w BB BV B w BB BV w BB BB B BB and Kazimierz Strzatka1 1Department of Plant Physiology and Biochemistry The Jan Zurzycki Institute of Molecular Biology and Biotechnology Jagiellonian University Krakow Poland 2H. Niewodniczanski Institute of Nuclear Physics Krakow Poland 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 of monogalactosyldiacylglycerol 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. .