GLUL and Hyperammonemia: Hyperammonemia is highly toxic for the brain and associated with encephalopathy and seizures, and NAD+ is important for numerous redox reactions in the cell.6, 29 Recently, a new biological function of GS for motility and migration of endothelial cells has been revealed, which contributes to the formation of new vessels in development and disease.30 Whether this plays a contributing role to the clinical phenotype of GS deficiency has not been elucidated yet.