College of Biotechnology, Tianjin University of Science & Technology, Key Laboratory of Industrial Microbiology of Education Ministry, Tianjin 300457, China.
Biotechnol Lett. 2013 May;35(5):735-41. doi: 10.1007/s10529-013-1138-1. Epub 2013 Jan 26.
Histidine biosynthesis in Corynebacterium glutamicum is regulated not only by feedback inhibition by the first enzyme in the pathway, but also by repression control of the synthesis of the histidine enzymes. C. glutamicum histidine genes are located and transcribed in two unlinked loci, hisEG and hisDCB-orf1-orf2-hisHA-impA-hisFI. We constructed plasmid pK18hisDPtac to replace the native hisD promoter with the tac promoter, and overexpressed phosphoribosyl-ATP-pyrophosphohydrolase, encoded by hisE, and ATP-phosphoribosyltransferase, encoded by hisG. The L-histidine titer at 0.85 g l(-1) was 80 % greater in the transformed bacterium and production of byproducts, L-alanine and L-tryptophan, was significantly decreased. However, accumulation of glutamic acid increased by 58 % (2.8 g l(-1)). This study represents the first attempt to substitute the histidine biosynthesis pathway promoter in the chromosome with a stronger promoter to increase histidine production.
谷氨酸棒杆菌中的组氨酸生物合成不仅受到途径中第一个酶的反馈抑制调节，还受到组氨酸酶合成的阻遏控制。谷氨酸棒杆菌的组氨酸基因位于两个不相关的基因座上，并转录为 hisEG 和 hisDCB-orf1-orf2-hisHA-impA-hisFI。我们构建了质粒 pK18hisDPtac，以 tac 启动子取代天然 hisD 启动子，并过表达由 hisE 编码的磷酸核糖基-ATP-焦磷酸水解酶和由 hisG 编码的 ATP-磷酸核糖基转移酶。转化菌中 L-组氨酸的产量达到 0.85 g l(-1)，增加了 80%，而副产物 L-丙氨酸和 L-色氨酸的产量则显著降低。然而，谷氨酸的积累增加了 58%（2.8 g l(-1)）。本研究首次尝试用更强的启动子替代染色体中组氨酸生物合成途径的启动子，以提高组氨酸的产量。
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