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Ammonia detoxification

Ammonia is detoxified through its conversion to urea by the enzymes in the small boxes, whose abbreviations are spelled out below. OTC catalyzes the synthesis of citrulline from carbamoyl phosphate and ornithine. Deficiency of OTC (highlighted in red) causes hyperammonemia along with accumulation of plasma glutamine and decreased plasma citrulline and arginine concentrations. Urinary orotic acid is markedly elevated. 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 2011.)

Associated Disorders

  • Ataxia
  • Carbamoyl phosphate synthetase 1 deficiency
  • Carbonic anhydrase VA deficiency
  • Carbonic anhydrase VA deficiency
  • Cerebral palsy
  • Congenital hyperammonemia
  • Hyperinsulinism-hyperammonemia syndrome
  • Intellectual disability
  • Maple syrup urine disease
  • N-acetylglutamate synthase deficiency
  • Neuropsychiatric disease
  • Reye syndrome
  • Seizure disorder
  • Urea cycle disorders (others)
  • Valproate toxicity