Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan.
Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka, 830-0011, Japan.
Photosynth Res. 2018 Mar;135(1-3):319-328. doi: 10.1007/s11120-017-0415-6. Epub 2017 Jun 22.
A chlorosome is a large and efficient light-harvesting antenna system found in some photosynthetic bacteria. This system comprises self-aggregates of bacteriochlorophyll (BChl) c, d, or e possessing a chiral 1-hydroxyethyl group at the 3-position, which plays a key role in the formation of the supramolecule. Biosynthesis of chlorosomal pigments involves stereoselective conversion of 3-vinyl group to 3-(1-hydroxyethyl) group facilitated by a 3-vinyl hydratase. This 3-vinyl hydration also occurs in BChl a biosynthesis, followed by oxidation that introduces an acetyl group at the 3-position. Herein, we present in vitro enzymatic assays of paralogous 3-vinyl hydratases derived from green sulfur bacteria, Chlorobaculum tepidum and Chlorobaculum limnaeum, the filamentous anoxygenic phototroph Chloroflexus aurantiacus, and the chloracidobacterium Chloracidobacterium thermophilum. All the hydratases showed hydration activities. The biosynthetic pathway of BChl a and other chlorosomal pigments is discussed considering the substrate specificity and stereoselectivity of the present hydratases.
一个叶绿素是一个大型和高效的光收集天线系统中发现的一些光合细菌。这个系统包括自我聚集的细菌叶绿素（叶绿素）c，d，或 e 拥有一个手性 1 -羟乙基在 3 -位置，在超分子的形成中起着关键作用。叶绿素的生物合成涉及到立体选择性的 3 -乙烯基转换为 3 -（1 -羟乙基）基团由 3 -乙烯基水合酶促进。这 3 -乙烯基水合也发生在 BChl 的生物合成中，随后的氧化在 3 -位置引入一个乙酰基。在这里，我们提出了来自绿硫细菌、Chlorobaculum tepidum 和 Chlorobaculum limnaeum、丝状厌氧光养生物 Chloroflexus aurantiacus 和 Chloracidobacterium thermophilum 的同源 3 -乙烯基水合酶的体外酶促测定。所有的水合酶都表现出水化活性。考虑到目前水合酶的底物特异性和立体选择性，讨论了 BChl 的生物合成途径和其他叶绿素的生物合成途径。
