Why metabolic enzymes are essential or nonessential for growth of Escherichia coli k12 on glucose
Why metabolic enzymes are essential or nonessential for growth of Escherichia coli k12 on glucose
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DOI：
10.1021/bi7014629
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发表时间：
2007-11-06
期刊：
影响因子：
2.9
通讯作者：
Copley, Shelley D.
中科院分区：
文献类型：
--
作者：
Kim, Juhan;Copley, Shelley D.
编码参与葡萄糖代谢、TCA循环以及氨基酸、嘌呤、嘧啶和辅因子的生物合成的代谢酶的基因预计对于大肠杆菌在葡萄糖上的生长是必不可少的，因为细胞必须合成细胞大分子的所有构件。令人惊讶的是，227个基因中有80个不是必需的。分析这些基因为什么不是必需的，可以深入了解大肠杆菌的代谢复杂性。大肠杆菌和形成其生理学的进化压力。通过互连路径启用的替代路由可以允许绕过有缺陷的步骤。同工酶、替代酶、广泛特异性酶和多功能酶通常可以替代缺失的酶。我们预期这些代谢途径中的明显冗余是由于需要E。大肠杆菌能够在各种生境中生存，因此具有能够最佳利用各种环境资源的新陈代谢，并在无法从环境中获得小分子时合成小分子。
The genes encoding metabolic enzymes involved in glucose metabolism, the TCA cycle, and biosynthesis of amino acids, purines, pyrimidines, and cofactors would be expected to be essential for growth of Escherichia coli on glucose because the cells must synthesize all of the building blocks for cellular macromolecules. Surprisingly, 80 of 227 of these, genes are not essential. Analysis of why these genes are not essential provides insights into the metabolic sophistication of E. coli and into the evolutionary pressures that have shaped its physiology. Alternative routes enabled by interconnecting pathways can allow a defective step to be bypassed. Isozymes, alternative enzymes, broad-specificity enzymes, and multifunctional enzymes can often substitute for a missing enzyme. We expect that the apparent redundancy in these metabolic pathways has arisen due to the need for E. coli to survive in a variety of habitats and therefore to have a metabolism that allows optimal exploitation of varying environmental resources and synthesis of small molecules when they cannot be obtained from the environment.