Flux balance analysis of primary metabolism in Chlamydomonas reinhardtii
Flux balance analysis of primary metabolism in Chlamydomonas reinhardtii
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DOI：
10.1186/1752-0509-3-4
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发表时间：
2009-01-07
影响因子：
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通讯作者：
Morgan, John A.
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文献类型：
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作者：
Boyle, Nanette R.;Morgan, John A.
背景：光合生物将大气中的二氧化碳转化为多种代谢物，形成新的生物量。水生光合生物几乎固定了全球一半的无机碳，具有巨大的潜力：作为二氧化碳固定方法，用于经济生产化学品，或作为脂质和淀粉的来源，然后可以转化为生物燃料。为了利用这一潜力，通过代谢工程和最大限度地提高产量，必须首先实现对光合代谢的更彻底的了解。以莱因哈蒂藻为模型藻类，重建了其代谢网络。然后使用通量平衡分析（FBA）计算细胞内通量。结果：利用基因组和生物化学信息，重建了莱茵青藻（c.r ainhardtii）初级代谢网络。重建的网络解释了酶在细胞内定位到三个区室，包括484种代谢反应和458种细胞内代谢物。基于BLAST检索，一个新标注的酶（果糖-1,6-双磷酸酶）被添加到莱茵衣藻数据库中。利用FBA预测自养、异养和混合养三种生长条件下的代谢通量。生物量产量从自养生长的28.9 g / mol C到异养生长的15 g / mol C不等。结论：莱茵青霉中、中间代谢通量平衡分析模型是第一个藻类代谢通量平衡模型，也是第一个包含三个代谢活性区室的模型。除了提供细胞内通量的估计外，代谢重建和建模工作还为基因组数据库的注释提供了一种全面的方法。我们的重建结果是，在数据库中注释了一个新的酶，而发现其他几个酶缺失；暗示新的途径或非保守的酶。利用FBA估计胞内通量也提供了通量值，可作为合理工程的起点。从这些初步估计来看，很明显，在醋酸盐上生长的好氧异养细胞的碳产量很低，而混合营养和自养生长的细胞的碳效率明显更高。
Background: Photosynthetic organisms convert atmospheric carbon dioxide into numerous metabolites along the pathways to make new biomass. Aquatic photosynthetic organisms, which fix almost half of global inorganic carbon, have great potential: as a carbon dioxide fixation method, for the economical production of chemicals, or as a source for lipids and starch which can then be converted to biofuels. To harness this potential through metabolic engineering and to maximize production, a more thorough understanding of photosynthetic metabolism must first be achieved. A model algal species, C. reinhardtii, was chosen and the metabolic network reconstructed. Intracellular fluxes were then calculated using flux balance analysis (FBA).Results: The metabolic network of primary metabolism for a green alga, C. reinhardtii, was reconstructed using genomic and biochemical information. The reconstructed network accounts for the intracellular localization of enzymes to three compartments and includes 484 metabolic reactions and 458 intracellular metabolites. Based on BLAST searches, one newly annotated enzyme (fructose-1,6-bisphosphatase) was added to the Chlamydomonas reinhardtii database. FBA was used to predict metabolic fluxes under three growth conditions, autotrophic, heterotrophic and mixotrophic growth. Biomass yields ranged from 28.9 g per mole C for autotrophic growth to 15 g per mole C for heterotrophic growth.Conclusion: The flux balance analysis model of central and intermediary metabolism in C. reinhardtii is the first such model for algae and the first model to include three metabolically active compartments. In addition to providing estimates of intracellular fluxes, metabolic reconstruction and modelling efforts also provide a comprehensive method for annotation of genome databases. As a result of our reconstruction, one new enzyme was annotated in the database and several others were found to be missing; implying new pathways or non-conserved enzymes. The use of FBA to estimate intracellular fluxes also provides flux values that can be used as a starting point for rational engineering of C. reinhardtii. From these initial estimates, it is clear that aerobic heterotrophic growth on acetate has a low yield on carbon, while mixotrophically and autotrophically grown cells are significantly more carbon efficient.