Lin Henry, San Ka-Yiu, Bennett George N
Department of Bioengineering MS 142, Rice University, Houston, TX 77251-1892, USA.
Appl Microbiol Biotechnol. 2005 Jun;67(4):515-23. doi: 10.1007/s00253-004-1789-x. Epub 2004 Nov 24.
Sorghum vulgare phosphoenolpyruvate carboxylase (PEPC) and Lactococcus lactis pyruvate carboxylase (PYC) were overexpressed in Escherichia coli concurrently to improve the production of succinate, a valuable industrial specialty chemical. This coexpression system was also applied to E. coli mutant strains strategically designed by inactivating the competing pathways of succinate formation. The highest level of succinate production was observed in E. coli strains coexpressing both PEPC and PYC when compared with E. coli strains individually overexpressing either PEPC or PYC. Lactate production was also significantly reduced with PEPC and PYC coexpression. Lactate and acetate pathways were inactivated to eliminate the competing pathways of succinate formation. Results showed that inactivation of both the lactate and acetate pathways with the coexpression of PEPC and PYC was most effective in improving succinate production. Inactivating the lactate or acetate pathway alone only caused a majority of the carbon flux to shift to other metabolites rather than succinate. Coexpression of PEPC and PYC was also applied to an E. coli mutant strain deficient in lactate dehydrogenase and pyruvate:formate lyase that accumulated a substantial amount of the intermediate metabolite pyruvate during growth. Results showed that PEPC and PYC coexpression was effective in depleting pyruvate accumulation and increasing the production of metabolites.
同时在大肠杆菌中过表达高粱磷酸烯醇式丙酮酸羧化酶（PEPC）和乳酸乳球菌丙酮酸羧化酶（PYC），以提高琥珀酸的产量，琥珀酸是一种有价值的工业特种化学品。该共表达系统还应用于通过使琥珀酸形成的竞争途径失活而经策略性设计的大肠杆菌突变菌株。与单独过表达PEPC或PYC的大肠杆菌菌株相比，在共表达PEPC和PYC的大肠杆菌菌株中观察到最高水平的琥珀酸产量。PEPC和PYC共表达也显著降低了乳酸的产生。使乳酸和乙酸途径失活以消除琥珀酸形成的竞争途径。结果表明，PEPC和PYC共表达使乳酸和乙酸途径均失活，这在提高琥珀酸产量方面最为有效。单独使乳酸或乙酸途径失活只会导致大部分碳通量转移到其他代谢物而不是琥珀酸。PEPC和PYC的共表达也应用于缺乏乳酸脱氢酶和丙酮酸：甲酸裂解酶的大肠杆菌突变菌株，该菌株在生长过程中积累了大量的中间代谢物丙酮酸。结果表明，PEPC和PYC共表达在消耗丙酮酸积累和增加代谢物产量方面是有效的。
