Mechanism of zinc-insertion into porphyrin ring in acidophilic photosynthetic bacteria

研究目的：本研究的最终目的是阐明嗜酸光合菌中锌-细菌-叶绿素的生物合成机制。结果和范围：1.在红色嗜酸杆菌中，镁螯合酶亚单位基因是单拷贝的，这些基因在该细菌中具有功能。细菌中只积累镁原卟啉IX及其单甲酯，而不积累锌原卟啉IX及其单甲酯。还检测到原卟啉IX单甲酯作为中间体。说明镁离子插入后与锌离子发生交换，形成锌细菌叶绿体。这种交换是在酶作用下还是在非酶作用下发生的尚不能确定，但在可能形成锌-细菌-叶绿素的低pH环境中，这种交换很容易发生，而且是非酶作用的。我们试图检测这种细菌中含有锌四吡咯的中间体，以确定交换反应，但到目前为止我们还不能。

The aim :Final aim of this research is to elucidate the mechanism of biosynthesis of zinc-bacteriochlorophyll in acidophilic photosynthetic bacteria.Results and scope :1. In Acidiphilium rubrum, there was a single copy of magnesium chelatase subunit genes and these were functional in this bacterium.2. Only magnesium-protoporphyrin IX and its monomethyl ester accumulated but not zinc-protoporphyrin IX or its monomethylester in the bacterium. Protoporphyrin IX monomethyl ester was also detected as an intermediate. These suggested magnesium was exchanged by zinc after magnesium insertion to form zinc-bacteriochlorophyll.3. Whether the exchange takes place in enzymatically or non-enzymatically could not be determined, but it was possible that in the low pH environment, where zinc-bacteriochlorophyll might be formed, the exchange take places very easily and non-enzymatically.4. We tried to detect intermediates containing zinc-tetrapyrroles in this bacterium to identify the exchange reaction but so far we could not.