Aiba S, Tsunekawa H, Imanaka T
Appl Environ Microbiol. 1982 Feb;43(2):289-97. doi: 10.1128/aem.43.2.289-297.1982.
For the purpose of studying the production of L-tryptophan by Escherichia coli, the deletion mutants of the trp operon (trpAE1) were transformed with mutant plasmids carrying the trp operon whose anthranilate synthase and phosphoribosyl anthranilate transferase (anthranilate aggregate), respectively, had been desensitized to tryptophan inhibition. In addition to release of the anthranilate aggregate from the feedback inhibition required for plasmids such as pSC101 trp.I15, the properties of trp repression (trpR) and tryptophanase deficiency (tnaA) were both indispensable for host strains such as strain Tna (trpAE1 trpR tnaA). The gene dosage effects on tryptophan synthase activities and on production of tryptophan were assessed. A moderate plasmid copy number, approximately five per chromosome, was optimal for tryptophan production. Similarly, an appropriate release of the anthranilate aggregate from feedback inhibition was also a necessary step to ward off the metabolic anomaly. If the mutant plasmid pSC101 trp-I15 was further mutagenized (pSC101 trp.I15.14) and then transferred to Tna cells, an effective enhancement of tryptophan production was achieved. Although further improvement of the host-plasmid system is needed before commercial production of tryptophan can be realized by this means, a promising step toward this goal has been established.
为了研究大肠杆菌生产L-色氨酸的情况，用携带色氨酸操纵子的突变质粒转化色氨酸操纵子（trpAE1）的缺失突变体，该色氨酸操纵子的邻氨基苯甲酸合酶和磷酸核糖基邻氨基苯甲酸转移酶（邻氨基苯甲酸聚合酶）分别对色氨酸抑制不敏感。除了像pSC101 trp.I15这样的质粒所需的邻氨基苯甲酸聚合酶从反馈抑制中释放出来外，色氨酸阻遏（trpR）和色氨酸酶缺陷（tnaA）的特性对于诸如Tna菌株（trpAE1 trpR tnaA）这样的宿主菌株都是必不可少的。评估了基因剂量对色氨酸合酶活性和色氨酸生产的影响。中等的质粒拷贝数，大约每条染色体五个，对于色氨酸生产是最佳的。同样，邻氨基苯甲酸聚合酶从反馈抑制中的适当释放也是避免代谢异常的必要步骤。如果将突变质粒pSC101 trp-I15进一步诱变（pSC101 trp.I15.14），然后转移到Tna细胞中，色氨酸产量会有效提高。尽管在用这种方法实现色氨酸的商业化生产之前，宿主-质粒系统还需要进一步改进，但已经朝着这个目标迈出了有希望的一步。
