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Ammonia is detoxified through its conversion to urea by the enzymes in the small boxes (abbreviations are indicated below). Arginase 1 catalyzes the hydrolysis of arginine to urea, which is excreted in the urine, and to ornithine, the substrate for ornithine transcarbamylase. Deficiency of arginase 1 (highlighted in red) may cause hyperammonemia along with accumulation of plasma glutamine and arginine. Increased urinary excretion of orotic acid and guanidino compounds can be found. NAGS, N-acetylglutamate synthase; CPS1, carbamoyl phosphate synthetase 1; OTC, ornithine transcarbamylase; ASS, argininosuccinate synthetase; ASL, argininosuccinate lyase; ARG1, arginase 1. (Adapted from Zschocke and Hoffmann 2020.)

Associated Disorders

  • Intellectual disability
  • Neuropsychiatric disease
  • Seizure disorder
  • Spastic para-/quadriplegia
  • Valproate toxicity