Gómez-García María R, Losada Manuel, Serrano Aurelio
Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla Cartuja, CSIC-Universidad de Sevilla, Spain.
FEBS J. 2007 Aug;274(15):3948-59. doi: 10.1111/j.1742-4658.2007.05927.x. Epub 2007 Jul 16.
Soluble inorganic pyrophosphatases (inorganic diphosphatases, EC 3.6.1.1) were isolated and characterized from three phylogenetically diverse cyanobacteria--Synechocystis sp. PCC 6803, Anabaena sp. PCC 7120, and Pseudanabaena sp. PCC 6903--and one anoxygenic photosynthetic bacterium, Rhodopseudomonas viridis (purple nonsulfur). These enzymes were found to be family I soluble inorganic pyrophosphatases with c. 20 kDa subunits with diverse oligomeric structures. The corresponding ppa genes were cloned and functionally validated by heterologous expression. Cyanobacterial family I soluble inorganic pyrophosphatases were strictly Mg(2+)-dependent enzymes. However, diverse cation cofactor dependence was observed for enzymes from other groups of photosynthetic bacteria. Immunochemical studies with antibodies to cyanobacterial soluble inorganic pyrophosphatases showed crossreaction with orthologs of other main groups of phototrophic prokaryotes and suggested a close relationship with the enzyme of heliobacteria, the nearest photosynthetic relatives of cyanobacteria. A slow-growing Escherichia coli JP5 mutant strain, containing a very low level of soluble inorganic pyrophosphatase activity, was functionally complemented up to wild-type growth rates with ppa genes from diverse photosynthetic prokaryotes expressed under their own promoters. Overall, these results suggest that the bacterial family I soluble inorganic pyrophosphatases described here have retained functional similarities despite their genealogies and their adaptations to diverse metabolic scenarios.
从三种系统发育不同的蓝细菌——聚球藻属PCC 6803、鱼腥藻属PCC 7120和伪鱼腥藻属PCC 6903——以及一种不产氧光合细菌绿假单胞菌（紫色非硫细菌）中分离并鉴定了可溶性无机焦磷酸酶（无机二磷酸酶，EC 3.6.1.1）。发现这些酶是I类可溶性无机焦磷酸酶，具有约20 kDa的亚基，且寡聚结构多样。克隆了相应的ppa基因，并通过异源表达进行了功能验证。蓝细菌I类可溶性无机焦磷酸酶是严格依赖Mg(2+)的酶。然而，观察到其他光合细菌组的酶对阳离子辅因子的依赖性不同。用针对蓝细菌可溶性无机焦磷酸酶的抗体进行的免疫化学研究表明，与其他主要光合原核生物组的直系同源物有交叉反应，并表明与蓝细菌最近的光合亲属——嗜光细菌的酶有密切关系。一种生长缓慢的大肠杆菌JP5突变株，其可溶性无机焦磷酸酶活性水平非常低，用来自不同光合原核生物且在其自身启动子下表达的ppa基因进行功能互补后，生长速率可恢复到野生型水平。总体而言，这些结果表明，尽管本文所述的细菌I类可溶性无机焦磷酸酶的谱系不同且适应不同的代谢情况，但它们仍保留了功能上的相似性。
