Argininosuccinate lyase deficiency

Genet Med. 2012 May;14(5):501-7. doi: 10.1038/gim.2011.1. Epub 2012 Jan 5.

Abstract

The urea cycle consists of six consecutive enzymatic reactions that convert waste nitrogen into urea. Deficiencies of any of these enzymes of the cycle result in urea cycle disorders (UCDs), a group of inborn errors of hepatic metabolism that often result in life-threatening hyperammonemia. Argininosuccinate lyase (ASL) catalyzes the fourth reaction in this cycle, resulting in the breakdown of argininosuccinic acid to arginine and fumarate. ASL deficiency (ASLD) is the second most common UCD, with a prevalence of ~1 in 70,000 live births. ASLD can manifest as either a severe neonatal-onset form with hyperammonemia within the first few days after birth or as a late-onset form with episodic hyperammonemia and/or long-term complications that include liver dysfunction, neurocognitive deficits, and hypertension. These long-term complications can occur in the absence of hyperammonemic episodes, implying that ASL has functions outside of its role in ureagenesis and the tissue-specific lack of ASL may be responsible for these manifestations. The biochemical diagnosis of ASLD is typically established with elevation of plasma citrulline together with elevated argininosuccinic acid in the plasma or urine. Molecular genetic testing of ASL and assay of ASL enzyme activity are helpful when the biochemical findings are equivocal. However, there is no correlation between the genotype or enzyme activity and clinical outcome. Treatment of acute metabolic decompensations with hyperammonemia involves discontinuing oral protein intake, supplementing oral intake with intravenous lipids and/or glucose, and use of intravenous arginine and nitrogen-scavenging therapy. Dietary restriction of protein and dietary supplementation with arginine are the mainstays in long-term management. Orthotopic liver transplantation (OLT) is best considered only in patients with recurrent hyperammonemia or metabolic decompensations resistant to conventional medical therapy.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Arginine / metabolism
  • Arginine / therapeutic use
  • Argininosuccinate Lyase / genetics
  • Argininosuccinic Acid / blood
  • Argininosuccinic Acid / metabolism
  • Argininosuccinic Acid / urine
  • Argininosuccinic Aciduria / diagnosis*
  • Argininosuccinic Aciduria / genetics*
  • Argininosuccinic Aciduria / therapy
  • Child, Preschool
  • Citrulline / blood
  • Cognition Disorders / enzymology
  • Cognition Disorders / genetics
  • Diet, Protein-Restricted
  • Fumarates / metabolism
  • Genetic Testing
  • Glucose / therapeutic use
  • Humans
  • Hyperammonemia / enzymology
  • Hyperammonemia / genetics
  • Hypertension / enzymology
  • Hypertension / genetics
  • Infant
  • Infant, Newborn
  • Lipids / therapeutic use
  • Liver Diseases / enzymology
  • Liver Diseases / genetics
  • Liver Transplantation
  • Neonatal Screening
  • Phenylbutyrates / therapeutic use
  • Sodium Benzoate / therapeutic use

Substances

  • Fumarates
  • Lipids
  • Phenylbutyrates
  • Argininosuccinic Acid
  • Citrulline
  • 4-phenylbutyric acid
  • Arginine
  • Argininosuccinate Lyase
  • Glucose
  • Sodium Benzoate