In Vitro Enzymatic Activity Assays Implicate the Existence of the Chlorophyll Cycle in Chlorophyll b-Containing Cyanobacteria
In Vitro Enzymatic Activity Assays Implicate the Existence of the Chlorophyll Cycle in Chlorophyll b-Containing Cyanobacteria
复制标题
体外酶活性测定表明含叶绿素 b 的蓝细菌中叶绿素循环的存在
DOI：
10.1093/pcp/pcz157
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发表时间：
2019
影响因子：
4.9
通讯作者：
Ito Hisashi
中科院分区：
文献类型：
--
作者：
Lim HyunSeok;Tanaka Ayumi;Tanaka Ryouichi;Ito Hisashi
在植物体内，叶绿素（Chl）和叶绿素（Chl）是通过叶绿素加氧酶、Chl还原酶（CBR）和7-羟甲基叶绿素还原酶（HCAR）三种酶的作用相互转化的。这些反应统称为Chl循环。在植物中，这种循环途径普遍存在，并在不同发育阶段对不同光照条件的适应中发挥重要作用。相比之下，只有有限数量的蓝藻物种产生Chlb，这些包括Prochlorococcus，Prochloron，ProchlorothrixandAcaryochloris。在这项研究中，我们调查了可能存在的Chl循环在Chlb合成蓝藻通过测试在体外酶活性的CBR和HCAR同源物从Prochlorothrix hollandica和AcaryochlorisRCC 1774。所有这些蛋白质在体外显示出各自的CBR和HCAR活性，表明这两种蓝藻都具有完成叶绿素循环的潜力。CBR和HCAR同源基因仅分布于光照条件动态变化的浅海或淡水中的含叶绿素b的蓝藻中，而在通常栖息于固定光照环境的原绿球藻中没有发现。两者合计，我们的研究结果暗示了一种可能性，叶绿素循环功能的光驯化含叶绿素b蓝藻。
In plants, chlorophyll (Chl)aandbare interconvertible by the action of three enzymes—chlorophyllideaoxygenase, Chlbreductase (CBR) and 7-hydroxymethyl chlorophyllareductase (HCAR). These reactions are collectively referred to as the Chl cycle. In plants, this cyclic pathway ubiquitously exists and plays essential roles in acclimation to different light conditions at various developmental stages. By contrast, only a limited number of cyanobacteria species produce Chlb, and these includeProchlorococcus,Prochloron,ProchlorothrixandAcaryochloris. In this study, we investigated a possible existence of the Chl cycle in Chlbsynthesizing cyanobacteria by testing in vitro enzymatic activities of CBR and HCAR homologs fromProchlorothrix hollandicaandAcaryochlorisRCC1774. All of these proteins show respective CBR and HCAR activity in vitro, indicating that both cyanobacteria possess the potential to complete the Chl cycle. It is also found that CBR and HCAR orthologs are distributed only in the Chlb-containing cyanobacteria that habitat shallow seas or freshwater, where light conditions change dynamically, whereas they are not found inProchlorococcusspecies that usually habitat environments with fixed lighting. Taken together, our results implicate a possibility that the Chl cycle functions for light acclimation in Chlb-containing cyanobacteria.