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Ammonia detoxification through conversion to urea by enzymes

Ammonia is detoxified through its conversion to urea by the enzymes in the small boxes, whose abbreviations are spelled out below. CPS1 catalyzes the synthesis of carbamoyl phosphate from bicarbonate, ammonia, and ATP. Deficiency of CPS1 (highlighted in red) causes hyperammonemia along with accumulation of plasma glutamine and decreased plasma citrulline and arginine levels. Urinary orotic acid is decreased or normal. 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
  • Carbonic anhydrase VA deficiency
  • Cerebral palsy
  • Congenital hyperammonemia
  • Hyperinsulinism-hyperammonemia syndrome
  • Intellectual disability
  • Maple syrup urine disease
  • N-acetylglutamate synthase deficiency
  • Neuropsychiatric disease
  • Organic acidurias
  • Reye syndrome
  • Seizure disorder
  • Urea cycle disorders (others)
  • Valproate toxicity