Navas M A, Gancedo J M
Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
J Bacteriol. 1996 Apr;178(7):1809-12. doi: 10.1128/jb.178.7.1809-1812.1996.
The question of how the loss of regulatory mechanisms for a metabolic enzyme would affect the fitness of the corresponding organism has been addressed. For this, the fructose-1,6-bisphosphatase (FbPase) from Saccharomyces cerevisiae has been taken as a model. Yeast strains in which different controls on FbPase (catabolite repression and inactivation; inhibition by fructose-2,6-bisphosphate and AMP) have been removed have been constructed. These strains express during growth on glucose either the native yeast FbPase, the Escherichia coli FbPase which is insensitive to inhibition by fructose-2,6-bisphosphate, or a mutated E. coli FbPase with low sensitivity to AMP. Expression of the heterologous FbPases increases the fermentation rate of the yeast and its generation time, while it decreases its growth yield. In the strain containing high levels of an unregulated bacterial FbPase, cycling between fructose-6-phosphate and fructose-1,6-bisphosphate reaches 14%. It is shown that the regulatory mechanisms of FbPase provide a slight but definite competitive advantage during growth in mixed cultures.
代谢酶调节机制的丧失如何影响相应生物体的适应性这一问题已得到探讨。为此，酿酒酵母的果糖-1,6-二磷酸酶（FbPase）被用作模型。构建了去除对FbPase的不同调控（分解代谢物阻遏和失活；果糖-2,6-二磷酸和AMP的抑制）的酵母菌株。这些菌株在以葡萄糖为碳源生长期间，要么表达天然酵母FbPase，要么表达对果糖-2,6-二磷酸抑制不敏感的大肠杆菌FbPase，要么表达对AMP低敏感性的突变大肠杆菌FbPase。异源FbPases的表达提高了酵母的发酵速率及其世代时间，同时降低了其生长产量。在含有高水平无调控细菌FbPase的菌株中，磷酸果糖激酶-1和果糖-1,6-二磷酸酶之间的循环达到14%。结果表明，FbPase的调节机制在混合培养物生长期间提供了轻微但确定的竞争优势。
