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

目的：本研究的最终目的是阐明嗜酸光合细菌合成锌细菌叶绿素的机制。在红色嗜酸菌中，镁螯合酶亚基基因只有一个拷贝，并且在该菌中具有功能.只有镁-原卟啉IX和它的单甲酯积累，但没有锌-原卟啉IX或其单甲酯的细菌。还检测到原卟啉IX单甲酯作为中间体。这说明镁离子插入后，锌离子交换镁离子，形成了锌-细菌叶绿素。虽然不能确定交换是在酶促还是非酶促条件下进行的，但在低pH环境下，锌-细菌叶绿素可能很容易发生交换，而且交换过程可能是非酶促的。我们试图检测该细菌中含有锌-四吡咯的中间体以鉴定交换反应，但到目前为止我们不能。

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.