Construction of Artificial Cells with Urea Cycle Pathway for Ammonia Detoxification

The bottom-up construction of artificial cells helps to understand cell working mechanisms. It is a great challenge to build artificial cells capable of detoxification. Herein, the urea cycle pathway is reconstituted inside artificial cells for ammonium detoxification. The urea cycle pathway involves carbamoyl phosphate synthetase, ornithine transcarbamylase, argininosuccinate synthetase, argininosuccinate lyase, and arginase, which converts NH₄HCO₃ to urea using a cyclic metabolic pathway. The urea is produced in a stepwise manner with the addition of NH₄HCO₃ when the cyclic metabolic reaction reaches equilibrium. The urea cycle pathway and NH₄HCO₃ are encapsulated into giant unilamellar vesicles to construct artificial cells capable of ammonium detoxification. The urea is produced inside artificial cells with the conversion rate of 61.9%. The concentration of extracellular NH₄HCO₃ is decreased from 20.0 to 2.3 mM with the addition of 1.5×10⁶ mL⁻¹ artificial cells, due to the inflow of NH₄HCO₃ through melittin pores in the membrane and subsequently metabolized by urea cycle pathway. It indicates the ammonium detoxification ability of artificial cells containing urea cycle pathway, which is further proved by rescuing Schwann cells in high concentration of NH₄HCO₃. This work paves a path to build functional artificial cells with more complicated metabolic networks for their biomedical applications.