菠菜细胞色素b_6f复合体中单线态氧的产生和清除机制(英文)

Singlet Oxygen Formation and Scavenging in Cytochrome b_6f Complex from Spinach

采用自旋捕捉电子顺磁共振技术研究了强光诱导下菠菜Cyt b6f中单线态氧(1O2*)产生和清除的分子机制,结果表明:在强光照射和有氧条件下,缺失Rieske Fe-S蛋白的Cytb6f和分离的Rieske Fe-S蛋白溶液中都检测到1O2*的产生,这证明Chla和Rieske Fe-S蛋白都是菠菜Cytb6f中光诱导1O2*产生的位点,而Chla是1O2*产生的主要部位。采用波长为675 nm的红光选择性激发Cytb6f中的Chla时,也检测到1O2*的产生,进一步支持了上述结论。此外,外加天然抗氧化物质,如抗坏血酸、谷胱甘肽、L-组氨酸和β-胡萝卜素,可清除系统中产生的1O2*。这很可能是菠菜Cytb6f中一种保护底物抵抗单线态氧光氧化的保护机制。

Electron spin resonance spectroscopy was used to study the mechanism of the singlet oxygen （1O2＊） production and scavenging in cytochrome b6f complex （Cyt bet） of spinach. The results showed that under white-light illumination and aerobic conditions, 1O2＊ was detected in isolated Rieske-depleted Cyt b6f and isolated Rieske Fe-S protein, indicating that both Chl a cofactor and Rieske Fe-S protein were responsible for 1O2＊ formation, with Chl a being the major source. This conclusion was further corroborated by 1O2＊ formation under selective excitation of Chl a by using monocolor red light at 675 nm. Furthermore, 1O2＊ was scavenged by adding antioxidative substance such as L-histidine, ascorbate, β-carotene or glutathione. This offered protection against singlet oxygen oxidation of Cyt bf complex.