Universität Rostock, Institut für Biowissenschaften, Abteilung Pflanzenphysiologie, Rostock, Germany.
Photosynth Res. 2011 Sep;109(1-3):103-14. doi: 10.1007/s11120-010-9615-z. Epub 2011 Jan 11.
The photorespiratory pathway was shown to be essential for organisms performing oxygenic photosynthesis, cyanobacteria, algae, and plants, in the present day O(2)-containing atmosphere. The identification of a plant-like 2-phosphoglycolate cycle in cyanobacteria indicated that not only genes of oxygenic photosynthesis but also genes encoding photorespiratory enzymes were endosymbiotically conveyed from ancient cyanobacteria to eukaryotic oxygenic phototrophs. Here, we investigated the origin of the photorespiratory pathway in photosynthetic eukaryotes by phylogenetic analysis. We found that a mixture of photorespiratory enzymes of either cyanobacterial or α-proteobacterial origin is present in algae and higher plants. Three enzymes in eukaryotic phototrophs clustered closely with cyanobacterial homologs: glycolate oxidase, glycerate kinase, and hydroxypyruvate reductase. On the other hand, the mitochondrial enzymes of the photorespiratory cycle in algae and plants, glycine decarboxylase subunits and serine hydroxymethyltransferase, evolved from proteobacteria. Other than most genes for proteins of the photosynthetic machinery, nearly all enzymes involved in the 2-phosphogylcolate metabolism coexist in the genomes of cyanobacteria and heterotrophic bacteria.
在当今含氧大气中，进行需氧光合作用的生物，如蓝藻、藻类和植物，其光呼吸途径被证明是必不可少的。在蓝藻中发现了一种类似于植物的 2-磷酸甘油酸循环，这表明不仅与需氧光合作用相关的基因，而且编码光呼吸酶的基因，都是从古老的蓝藻共生体传递给真核需氧光合生物的。在这里，我们通过系统发育分析研究了光合真核生物光呼吸途径的起源。我们发现，藻类和高等植物中存在着源自蓝藻或α-变形菌的混合光呼吸酶。真核光合生物中的三种酶与蓝藻同源物紧密聚类：乙醇酸氧化酶、甘油激酶和羟丙酮酸还原酶。另一方面，藻类和植物光呼吸循环中的线粒体酶，甘氨酸脱羧酶亚基和丝氨酸羟甲基转移酶，是从变形菌进化而来的。除了光合作用机制的大多数蛋白质基因外，2-磷酸甘油酸代谢中涉及的几乎所有酶都共存于蓝藻和异养细菌的基因组中。
