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The function of PROTOPORPHYRINOGEN IX OXIDASE in chlorophyll biosynthesis requires oxidised plastoquinone in Chlamydomonas reinhardtii.
Communications Biology ( IF 5.2 ) Pub Date : 2019-05-03 , DOI: 10.1038/s42003-019-0395-5
Pawel Brzezowski 1, 2 , Brigitte Ksas 3 , Michel Havaux 3 , Bernhard Grimm 2 , Marie Chazaux 1 , Gilles Peltier 1 , Xenie Johnson 1 , Jean Alric 1
Affiliation  

In the last common enzymatic step of tetrapyrrole biosynthesis, prior to the branching point leading to the biosynthesis of heme and chlorophyll, protoporphyrinogen IX (Protogen) is oxidised to protoporphyrin IX (Proto) by protoporphyrinogen IX oxidase (PPX). The absence of thylakoid-localised plastid terminal oxidase 2 (PTOX2) and cytochrome b 6 f complex in the ptox2 petB mutant, results in almost complete reduction of the plastoquinone pool (PQ pool) in light. Here we show that the lack of oxidised PQ impairs PPX function, leading to accumulation and subsequently uncontrolled oxidation of Protogen to non-metabolised Proto. Addition of 3(3,4-Dichlorophenyl)-1,1-dimethylurea (DCMU) prevents the over-reduction of the PQ pool in ptox2 petB and decreases Proto accumulation. This observation strongly indicates the need of oxidised PQ as the electron acceptor for the PPX reaction in Chlamydomonas reinhardtii. The PPX-PQ pool interaction is proposed to function as a feedback loop between photosynthetic electron transport and chlorophyll biosynthesis.

中文翻译:


原卟啉原 IX 氧化酶在叶绿素生物合成中的功能需要莱茵衣藻中的氧化质体醌。



在四吡咯生物合成的最后一个常见酶促步骤中,在导致血红素和叶绿素生物合成的分支点之前,原卟啉原 IX (Protogen) 被原卟啉原 IX 氧化酶 (PPX) 氧化为原卟啉 IX (Proto)。 ptox2 petB 突变体中类囊体定位的质体末端氧化酶 2 (PTOX2) 和细胞色素 b 6 f 复合物的缺失导致质体醌池 (PQ 池) 在光照下几乎完全减少。在这里,我们发现氧化 PQ 的缺乏会损害 PPX 功能,导致 Protogen 积累并随后不受控制地氧化为非代谢的 Proto。添加 3(3,4-二氯苯基)-1,1-二甲基脲 (DCMU) 可防止 ptox2 petB 中 PQ 池的过度还原并减少 Proto 积累。这一观察结果强烈表明莱茵衣藻中需要氧化 PQ 作为 PPX 反应的电子受体。 PPX-PQ 库相互作用被认为充当光合电子传递和叶绿素生物合成之间的反馈回路。
更新日期:2019-05-16
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