Bioengineering of photosynthetic membranes. Requirement of magnesium for the conversion of chlorophyllide a to chlorophyll a during the greening of etiochloroplasts in vitro
Bioengineering of photosynthetic membranes. Requirement of magnesium for the conversion of chlorophyllide a to chlorophyll a during the greening of etiochloroplasts in vitro
复制标题
光合膜生物工程。
DOI：
10.1002/bit.260260512
复制
发表时间：
1984
影响因子：
3.8
通讯作者：
C. Rebeiz
中科院分区：
文献类型：
--
作者：
H. Daniell;C. Rebeiz
δ-氨基乙酰丙酸 (ALA) 大量转化为原叶绿素内酯 (Pchlide) 和叶绿素 a (Chlide a) 大量转化为叶绿素 a (Chl a) 是 ALA 依赖性光合膜体外组装的两个必要条件。在这项工作中，我们描述了一种无细胞系统的开发，该系统能够在黑暗孵育的前 2 小时内以高于体内的速率进行上述生物合成活动。无细胞系统由以下部分组成：(1) 由激动素和赤霉酸预处理的黄瓜子叶制备的叶绿体，以及 (2) 其他地方描述的辅助因子和添加剂，它们是 ALA 大规模转化为 Pchlide 所必需的，(3) Chlide a 大规模转化为 Chl a 需要高浓度的 ATP、MgCl2 和异戊二烯醇（例如植醇）。还证明了氯化物 a 转化为叶绿素 a 时对 Mg2+ 的绝对且新颖的需求。植醇除了作为 Chlide a 转化为 Chl a 的底物的作用外，数据表明这种醇还可能参与 ALA 和 Pchlide 之间反应的调节。据推测，在绿化过程中，叶绿素 a 向叶绿素 a 的转化可能遵循不同的生物合成速率，具有不同的底物和辅因子需求，具体取决于质体发育的阶段。
The massive conversion of δ‐aminolevulinic acid (ALA) to protochlorophyllide (Pchlide) and the massive conversion of chlorophyllide a (Chlide a) to chlorophyll a (Chl a) are two essential conditions for the ALA‐dependent assembly of photosynthetic membranes in vitro. In this work, we describe the development of a cell‐free system capable of the forementioned biosynthetic activities at rates higher than in vivo, for the first 2 h of dark‐incubation. The cell‐free system consisted of (1) etiochloroplasts prepared from kinetin and gibberellic‐acid‐pretreated cucumber cotyledons, and (2) cofactors and additives described elsewhere and which are needed for the massive conversion of ALA to Pchlide, (3) high concentrations of ATP, MgCl2, and an isoprenol alcohol such as phytol, were required for the massive conversion of Chlide a to Chl a. An absolute and novel requirement of Mg2+ for the conversion of Chlide a to Chl a was also demonstrated. In addition to the role of phytol as a substrate for the conversion of Chlide a to Chl a, the data suggested that this alcohol may also be involved in the regulation of the reactions between ALA and Pchlide. It is proposed that during greening, the conversion of Chlide a to Chl a may follow different biosynthetic rates, having different substrate and cofactor requirements, depending on the stage of plastid development.