塑料醌
光磷酸化
电子传输链
光化学
光系统I
化学
细胞色素b6f复合物
电子受体
铁氧还蛋白
铁氰化物
光系统II
叶绿体
700页
电子转移
希尔反应
电子供体
光系统
类囊体
光合作用
生物化学
催化作用
酶
基因
作者
S. Izawa,J.Michael Gould,Donald R. Ort,Peter Felker,Norman E. Good
标识
DOI:10.1016/0005-2728(73)90237-5
摘要
Dibromothymoquinone (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone) is reputed to be a plastoquinone antagonist which prevents the photoreduction of hydrophilic oxidants such as ferredoxin-NADP+. However, we have found that dibromothymoquinone inhibits only a small part of the photoreduction of lipophilic oxidants such as oxidized p-phenylenediamine. Dibromothymoquinone-resistant photoreduction reactions are coupled to phosphorylation, about 0.4 molecules of ATP consistently being formed for every pair of electrons transported. Dibromothymoquinone itself is a lipophilic oxidant which can be photoreduced by chloroplasts, then reoxidized by ferricyanide or oxygen. The electron transport thus catalysed also supports phosphorylation and the Pe2 ratio is again 0.4. It is concluded that there is a site of phosphorylation before the dibromothymoquinone block and another site of phosphorylation after the block. The former site must be associated with electron transfer reactions near Photosystem II, while the latter site is presumably associated with the transfer of electrons from plastoquinone to cytochrome f.
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