Colón G E, Jetten M S, Nguyen T T, Gubler M E, Follettie M T, Sinskey A J, Stephanopoulos G
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge 02139.
Appl Environ Microbiol. 1995 Jan;61(1):74-8. doi: 10.1128/aem.61.1.74-78.1995.
Amplification of the operon homdr-thrB encoding a feedback-insensitive homoserine dehydrogenase and a wild-type homoserine kinase in a Corynebacterium lactofermentum lysine-producing strain resulted in both homoserine and threonine accumulation, with some residual lysine production. A plasmid enabling separate transcriptional control of each gene was constructed to determine the effect of various enzyme activity ratios on metabolite accumulation. By increasing the activity of homoserine kinase relative to homoserine dehydrogenase activity, homoserine accumulation in the medium was essentially eliminated and the final threonine titer was increased by about 120%. Furthermore, a fortuitous result of the cloning strategy was an unexplained increase in homoserine dehydrogenase activity. This resulted in a further decrease in lysine production along with a concomitant increase in threonine accumulation.
在产赖氨酸的乳酸发酵棒杆菌菌株中，对编码反馈不敏感型高丝氨酸脱氢酶和野生型高丝氨酸激酶的操纵子homdr-thrB进行扩增，导致高丝氨酸和苏氨酸积累，同时仍有一些赖氨酸产生。构建了一个能对每个基因进行单独转录控制的质粒，以确定各种酶活性比率对代谢物积累的影响。通过提高高丝氨酸激酶相对于高丝氨酸脱氢酶的活性，培养基中的高丝氨酸积累基本消除，最终苏氨酸产量提高了约120%。此外，克隆策略的一个意外结果是高丝氨酸脱氢酶活性出现了无法解释的增加。这导致赖氨酸产量进一步下降，同时苏氨酸积累增加。
