【午間科學講壇】週二 (6/20) Prof. Dr. Kazimierz Strzalka：Xanthophyll cycle – a plant way to cope with oxidative stress
在本學期最後一次，6月20日（下週二，非週四）本系【午間科學講壇】，感謝楊健志老師和化工系王勝仕老師的聯合安排，很榮幸地，邀請到波蘭克拉科夫，亞捷隆大學植物生理生化學系的資深權威教授 Prof. Dr. Kazimierz Strzalka 光臨本系，針對在強光和 Oxidative stress 下，胞內大量產生的 ROS (Reactive oxygen species) 對光合作用相關胞器之損害，植物如何因應、保護，發表其多年研究成果和觀點。講題是：
Xanthophyll cycle – a plant way to cope with oxidative stress亞捷隆大學是位於波蘭克拉科夫的研究型大學，為波蘭第一所大學，由卡齊米日三世創建於1364年，並在1400年由雅蓋沃國王復興 (ref: Wikipedia)。著名的天主教若望·保祿二世，就是此校之校友。Prof. Dr. Strzalka 從 1974年在其母系任教至今，是十分受到重視和仰望的學者。請不要錯過這次寶貴的學術交流機會。
Xanthophyll cycle – a plant way to cope with oxidative stress.
Reactive oxygen species formed during oxidative stress in high light conditions may heavily damage the photosynthetic apparatus. One of the efficient protective mechanisms against the oxidative damage is the xanthophyll cycle, occurring in all vascular plants and in many groups of algae. Two enzymes of the cycle: violaxanthin de-epoxidase and zeaxanthin epoxidase catalyze interconversion between the xanthophylls - violaxanthin, antheraxanthin and zeaxanthin, in response to changing light conditions. In low light and in darkness plants accumulate violaxanthin which serves as antenna. In high light-exposed plants zeaxanthin is formed which dissipates the excess of the absorbed energy as heat and also is a potent scavenger of the reactive oxygen species generated in the photosynthetic membranes under high light stress.
We demonstrated that rate of antheraxanthin and zeaxanthin formation from violaxanthin strongly depends on physical-chemical properties of thylakoid lipids. The key role for enzyme activation play non-bilayer lipids and the parameters of inverted micelles created by them, such as thickness, molecular dynamics of hydrophobic core and their diameter. Solubilization of pigments by lipids, mutual orientation of enzyme and substrate molecules as well as concentration of the main thylakoid lipid, monogalactosyldiacylglycerol, associated with light harvesting complex LHCII are postulated as main factors to explain the obtained results. Molecular mechanism of the xanthophyll cycle and its role in protection of plants against oxidative stress will be discussed.