Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Japan.
Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan.
FEBS Lett. 2019 Apr;593(8):799-809. doi: 10.1002/1873-3468.13372. Epub 2019 Apr 4.
We report the in vitro activity of recombinant BchC oxidoreductase involved in bacteriochlorophyll a biosynthesis. BchC of Rhodobacter capsulatus preferentially oxidizes 3 R-3-(1-hydroxyethyl)-chlorophyllide a and 3 R-3-(1-hydroxyethyl)-bacteriochlorophyllide a in the presence of NAD to 3-acetyl-chlorophyllide a and bacteriochlorophyllide a, respectively, leaving the unreacted 3 S-epimers. In the reverse reaction, BchC with NADH predominately produces 3 R-epimeric alcohols from the 3-acetyl-(bacterio)chlorins. BchC of Chlorobaculum tepidum demonstrates the same 3 R-selectivity, suggesting that utilization of 3 R-epimers in BchC-catalyzed reductions may be conserved across different phyla of photosynthetic bacteria. Additionally, the presence of BchC accelerates the 3-vinyl hydration by BchF hydratase of Chlorobaculum tepidum during conversion of chlorophyllide a to 3-acetyl-chlorophyllide a through 3-(1-hydroxyethyl)-chlorophyllide a, indicating that these enzymes work cooperatively to promote efficient bacteriochlorophyll a biosynthesis.
我们报告了参与细菌叶绿素 a 生物合成的重组 BchC 氧化还原酶的体外活性。荚膜红细菌的 BchC 在 NAD 的存在下优先氧化 3R-3-(1-羟乙基）叶绿素 a 和 3R-3-(1-羟乙基）细菌叶绿素 a，分别生成 3-乙酰叶绿素 a 和细菌叶绿素 a，而未反应的 3S-差向异构体则保留下来。在相反的反应中，BchC 与 NADH 主要从 3-乙酰-（细菌）胆绿素中产生 3R-差向异构体醇。来自嗜热盐杆菌的 BchC 表现出相同的 3R-选择性，表明在 BchC 催化的还原反应中，3R-差向异构体的利用可能在不同的光合细菌门中得到保守。此外，BchC 的存在加速了嗜热盐杆菌中 BchF 水合酶的 3-乙烯基水合作用，通过 3-(1-羟乙基）叶绿素 a 转化为 3-乙酰叶绿素 a，表明这些酶协同工作，以促进有效的细菌叶绿素 a 生物合成。
