Center for Microbial Biotechnology (CMB), Department of Systems Biology, Building 223, Technical University of Denmark (DTU), DK-2800 Kgs. Lyngby, Denmark.
Metab Eng. 2009 Nov;11(6):328-34. doi: 10.1016/j.ymben.2009.07.001. Epub 2009 Jul 18.
A genome-scale metabolic model was used to identify new target genes for enhanced biosynthesis of sesquiterpenes in the yeast Saccharomyces cerevisiae. The effect of gene deletions on the flux distributions in the metabolic model of S. cerevisiae was assessed using OptGene as the modeling framework and minimization of metabolic adjustments (MOMA) as objective function. Deletion of NADPH-dependent glutamate dehydrogenase encoded by GDH1 was identified as the best target gene for the improvement of sesquiterpene biosynthesis in yeast. Deletion of this gene enhances the available NADPH in the cytosol for other NADPH requiring enzymes, including HMG-CoA reductase. However, since disruption of GDH1 impairs the ammonia utilization, simultaneous over-expression of the NADH-dependent glutamate dehydrogenase encoded by GDH2 was also considered in this study. Deletion of GDH1 led to an approximately 85% increase in the final cubebol titer. However, deletion of this gene also caused a significant decrease in the maximum specific growth rate. Over-expression of GDH2 did not show a further effect on the final cubebol titer but this alteration significantly improved the growth rate compared to the GDH1 deleted strain.
利用基因组规模的代谢模型，鉴定了用于增强酵母酿酒酵母中倍半萜生物合成的新靶基因。使用 OptGene 作为建模框架和代谢调整最小化 (MOMA) 作为目标函数，评估了基因缺失对酿酒酵母代谢模型中通量分布的影响。鉴定出 NADPH 依赖性谷氨酸脱氢酶编码的 GDH1 的缺失是改善酵母中倍半萜生物合成的最佳靶基因。该基因的缺失增强了细胞质中其他需要 NADPH 的酶（包括 HMG-CoA 还原酶）的可用 NADPH。然而，由于 GDH1 的破坏会损害氨的利用，因此在本研究中还考虑了 NADH 依赖性谷氨酸脱氢酶编码的 GDH2 的过表达。GDH1 的缺失导致最终古巴醇产量增加了约 85%。然而，该基因的缺失也导致最大比生长速率显著下降。GDH2 的过表达对最终古巴醇产量没有进一步的影响，但与 GDH1 缺失株相比，这种改变显著提高了生长速率。
