Teixeira de Mattos M J, Neijssel O M
E.C. Slater Institute for Biochemistry and Microbiology, University of Amsterdam, The Netherlands.
J Biotechnol. 1997 Dec 17;59(1-2):117-26. doi: 10.1016/s0168-1656(97)00174-0.
A striking property of many prokaryotes is their enormous metabolic flexibility with respect not only to catabolic and anabolic substrates but also with respect to the continuously changing availability of nutrients. The phenotypic responses to low-nutrient growth conditions involve structural changes in the cellular make-up, changes in the specific capacity of the enzyme system(s) involved in uptake and/or assimilation of the limiting nutrient and changes in the affinity of these enzymes. Here the responses of some members of the Enterobacteriaceae to potassium-, ammonium- and energy source-limited conditions will be reviewed. The focus will be on the energetic consequences of these adaptations as reflected by the growth yield value for the energy source (Y energy source). It will be illustrated that Y energy source values can be dramatically lowered as a result of incomplete oxidation of the energy source (overflow metabolism), bypassing potential sites of energy conservation (uncoupling) or catabolic cycles that have no other apparent effect than the hydrolysis of ATP (futile cycles). Thus, it is concluded that adaptation to low nutrient conditions aims at maintaining high metabolic fluxes at low nutrient concentrations at the cost of a loss in the energetic efficiency of the overall metabolism.
许多原核生物的一个显著特性是其巨大的代谢灵活性，这不仅体现在分解代谢和合成代谢底物方面，还体现在营养素可利用性的不断变化上。对低营养生长条件的表型反应涉及细胞组成的结构变化、参与摄取和/或同化限制性营养素的酶系统的比活性变化以及这些酶亲和力的变化。在此将综述肠杆菌科一些成员对钾、铵和能源限制条件的反应。重点将放在这些适应性变化对能量的影响上，这通过能源的生长得率值（Y能源）来体现。将说明由于能源的不完全氧化（溢流代谢）、绕过潜在的能量守恒位点（解偶联）或除了ATP水解外没有其他明显作用的分解代谢循环（无效循环），Y能源值可能会显著降低。因此，可以得出结论，对低营养条件的适应旨在以整体代谢能量效率的损失为代价，在低营养浓度下维持高代谢通量。
