[Therapeutic efficacy of ASS1 combined with LOLA in the treatment of hyperammonemia in mice].

objectivesArgininosuccinate synthase 1 (ASS1) is a key rate-limiting enzyme in the urea cycle and is highly conserved at the protein level. Its catalytic activity directly determines the efficiency of ammonia clearance. Hyperammonemia is a clinical syndrome caused by abnormally elevated blood ammonia levels and is characterized mainly by central nervous system dysfunction, with neurotoxicity and a high mortality rate. When liver function is impaired or key enzymes of the urea cycle are deficient, ammonia clearance is reduced, leading to ammonia accumulation and passage across the blood-brain barrier, resulting in disturbances of consciousness, coma, or even death. Among currently used ammonia-lowering agents,

methodsThe full-length open reading frame of human ASS1 was amplified by reverse transcription polymerase chain reaction (RT-PCR), and both the PCR product and the pET-28a vector were digested with restriction enzymes. After purification by agarose gel electrophoresis, the pET-28a-

resultsThe pET28a-ASS1 vector was successfully constructed using homologous recombination, and soluble recombinant ASS1 protein was obtained in a prokaryotic expression system. After purification and concentration by Ni-NTA affinity chromatography, the protein purity reached 95.4%±1.2%, with a concentration of (10.5± 0.8) mg/mL. In vitro enzyme activity assays systematically characterized the enzymatic properties of ASS1, showing an optimal reaction temperature of 37 ℃ and an optimal pH of 8.0. Using Asp and Cit as substrates, the enzymatic kinetic parameters were determined. The

conclusionsRecombinant ASS1 protein obtained by prokaryotic expression exhibits stable and well-defined biological activity, with catalytic function significantly influenced by temperature and pH and displaying clear enzymatic kinetic characteristics. In an NH4Cl-induced mouse model of hyperammonemia, combined application of ASS1 and LOLA showed a more stable and effective ammonia-lowering effect than monotherapy, demonstrating good synergistic effects. These findings provide a new enzymatic intervention strategy for the treatment of hyperammonemia, lay a theoretical foundation for the development of combination ammonia-lowering therapies, and indicate potential application prospects.