As an essential metabolite in the urea cycle, lack of or decreased CP production due to CPS I deficiency [150], lack of the activator NAG due to N-acetyl-glutamate synthase (NAGS) deficiency [151], or decreased supply of carbon dioxide due to carbonic anhydrase VA deficiency [152] will disrupt the urea cycle resulting in hyperammonemia. The gene discussed is NAGS; the disease is Hyperammonemia.