ATP Drives Efficient Terpene Biosynthesis in Marine Thraustochytrids

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 conditions in their natural environment. However, the mechanism behind 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 metabolite limitation in the nondecarboxylative Claisen condensation of acetyl-coenzyme A (CoA) to the 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. Proteomic and metabolomic analyses further show that the increased ATP demands are fulfilled by shifting energy generation from carbohydrate to lipid oxidation. This study demonstrates a unique strategy in nature that uses ATP to drive a low-flux metabolic pathway, providing an alternative solution for efficient terpene metabolic engineering.