Li Man, Long Bin, Dai Susie Y, Golden James W, Wang Xin, Yuan Joshua S
Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, Texas 77843, USA.
Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas 77843, USA.
Biodes Res. 2022 Feb 7;2022:9897425. doi: 10.34133/2022/9897425. eCollection 2022.
Photosynthetic terpene production represents one of the most carbon and energy-efficient routes for converting CO into hydrocarbon. In photosynthetic organisms, metabolic engineering has led to limited success in enhancing terpene productivity, partially due to the low carbon partitioning. In this study, we employed systems biology analysis to reveal the strong competition for carbon substrates between primary metabolism (e.g., sucrose, glycogen, and protein synthesis) and terpene biosynthesis in PCC 7942. We then engineered key "source" and "sink" enzymes. The "source" limitation was overcome by knocking out either sucrose or glycogen biosynthesis to significantly enhance limonene production altered carbon partitioning. Moreover, a fusion enzyme complex with geranyl diphosphate synthase (GPPS) and limonene synthase (LS) was designed to further improve pathway kinetics and substrate channeling. The synergy between "source" and "sink" achieved a limonene titer of 21.0 mg/L. Overall, the study demonstrates that balancing carbon flux between primary and secondary metabolism can be an effective approach to enhance terpene bioproduction in cyanobacteria. The design of "source" and "sink" synergy has significant potential in improving natural product yield in photosynthetic species.
光合萜类化合物的生产是将二氧化碳转化为碳氢化合物的最具碳和能源效率的途径之一。在光合生物中，代谢工程在提高萜类化合物生产力方面取得的成功有限，部分原因是碳分配较低。在本研究中，我们采用系统生物学分析来揭示集胞藻PCC 7942中初级代谢（如蔗糖、糖原和蛋白质合成）与萜类生物合成之间对碳底物的激烈竞争。然后，我们对关键的“源”和“汇”酶进行了工程改造。通过敲除蔗糖或糖原生物合成来克服“源”限制，从而通过改变碳分配显著提高柠檬烯产量。此外，设计了一种由香叶基二磷酸合酶（GPPS）和柠檬烯合酶（LS）组成的融合酶复合物，以进一步改善途径动力学和底物通道化。“源”和“汇”之间的协同作用使柠檬烯滴度达到了21.0毫克/升。总体而言，该研究表明，平衡初级代谢和次级代谢之间的碳通量可能是提高蓝藻中萜类生物生产的有效方法。“源”和“汇”协同作用的设计在提高光合物种中天然产物产量方面具有巨大潜力。
