Department of Biopharmaceutic Engineering, School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China.
Appl Microbiol Biotechnol. 2013 Mar;97(5):1963-71. doi: 10.1007/s00253-012-4062-8. Epub 2012 May 29.
Dihydrodipicolinate synthase (DHDPS, EC 4.2.1.52) catalyzes the first committed reaction of L-lysine biosynthesis in bacteria and plants and is allosterically regulated by L-lysine. In previous studies, DHDPSs from different species were proved to have different sensitivity to L-lysine inhibition. In this study, we investigated the key determinants of feedback regulation between two industrially important DHDPSs, the L-lysine-sensitive DHDPS from Escherichia coli and L-lysine-insensitive DHDPS from Corynebacterium glutamicum, by sequence and structure comparisons and site-directed mutation. Feedback inhibition of E. coli DHDPS was successfully alleviated after substitution of the residues around the inhibitor's binding sites with those of C. glutamicum DHDPS. Interestingly, mutagenesis of the lysine binding sites of C. glutamicum DHDPS according to E. coli DHDPS did not recover the expected feedback inhibition but an activation of DHDPS by L-lysine, probably due to differences in the allosteic signal transduction in the DHDPS of these two organisms. Overexpression of L-lysine-insensitive E. coli DHDPS mutants in E. coli MG1655 resulted in an improvement of L-lysine production yield by 46 %.
二氢二吡啶羧酸合酶（DHDPS，EC 4.2.1.52）催化细菌和植物中赖氨酸生物合成的第一个关键反应，并且受到赖氨酸的变构调节。在以前的研究中，来自不同物种的 DHDPS 被证明对赖氨酸抑制具有不同的敏感性。在这项研究中，我们通过序列和结构比较以及定点突变，研究了两种工业上重要的 DHDPS（来自大肠杆菌的赖氨酸敏感型 DHDPS 和来自谷氨酸棒杆菌的赖氨酸不敏感型 DHDPS）之间反馈调节的关键决定因素。在用谷氨酸棒杆菌 DHDPS 的抑制剂结合位点周围的残基取代大肠杆菌 DHDPS 后，成功缓解了大肠杆菌 DHDPS 的反馈抑制。有趣的是，根据大肠杆菌 DHDPS 对谷氨酸棒杆菌 DHDPS 的赖氨酸结合位点进行诱变并没有恢复预期的反馈抑制，而是导致赖氨酸对 DHDPS 的激活，这可能是由于这两种生物体的 DHDPS 中变构信号转导的差异所致。在大肠杆菌 MG1655 中过表达赖氨酸不敏感的大肠杆菌 DHDPS 突变体，可使赖氨酸的产量提高 46%。
