Understanding carbon flux-controlling mechanisms in a tangled metabolic network is an essential question of cell metabolism. Secondary metabolism, such as terpene biosynthesis, has evolved with low carbon flux due to inherent pathway constraints. Thraustochytrids are a group of heterotrophic marine unicellular protists, and can accumulate terpenoids under the high salt condition in their natural environment. However, the mechanism behind the terpene accumulation is not well understood. Here we show that terpene biosynthesis in Thraustochytrium sp. ATCC 26185 is constrained by local thermodynamics in the mevalonate pathway. Thermodynamic analysis reveals the metabolite limitation in the nondecarboxylative Claisen condensation of acetyl-CoA to acetoacetyl-CoA step catalyzed by the acetyl-CoA acetyltransferase (ACAT). Through a sodium elicited mechanism, higher respiration leads to increased ATP investment into the mevalonate pathway, providing a strong thermodynamic driving force for enhanced terpene biosynthesis. The proteomic analysis further indicates that the increased ATP demands are fulfilled by shifting energy generation from carbohydrate to lipid metabolism. This study demonstrates a unique strategy in nature using ATP to drive a low-flux metabolic pathway, providing an alternative solution for efficient terpene metabolic engineering.

中文翻译：

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ATP在海洋破囊壶菌中驱动有效的萜烯生物合成

了解缠结的代谢网络中的碳通量控制机制是细胞代谢的基本问题。由于固有的途径限制，诸如萜烯生物合成之类的次生代谢以低碳通量发展。破囊壶菌是一组异养海洋单细胞质子体，可以在自然环境中的高盐条件下积聚萜类化合物。但是，关于萜烯积累的机理尚不十分清楚。在这里，我们显示了Thraustochytrium sp中的萜烯生物合成。甲羟戊酸途径中的局部热力学限制了ATCC 26185。热力学分析揭示了在乙酰辅酶A乙酰转移酶（ACAT）催化下，乙酰辅酶A至羧乙酰辅酶A的非脱羧性克莱森缩合反应中的代谢物限制。通过钠引起的机制，更高的呼吸作用导致甲羟戊酸途径中的ATP投资增加，从而为增强萜烯的生物合成提供了强大的热力学驱动力。蛋白质组学分析进一步表明，通过将能量产生从碳水化合物代谢转变为脂质代谢，可以满足增加的ATP需求。这项研究表明自然界中使用ATP驱动低通量代谢途径的独特策略，为有效的萜烯代谢工程提供了替代解决方案。