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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed March 2007

What is the official name of the ASL gene?

The official name of this gene is “argininosuccinate lyase.”

ASL is the gene's official symbol. The ASL gene is also known by other names, listed below.

What is the normal function of the ASL gene?

The ASL gene provides instructions for making the protein argininosuccinate lyase. This enzyme participates in the urea cycle, a series of reactions that occur in liver cells. The urea cycle processes excess nitrogen, generated when protein is used by the body, to make a compound called urea that is excreted by the kidneys. Excreting the excess nitrogen prevents it from accumulating in the form of ammonia.

The specific role of the ASL enzyme is to start the reaction in which the amino acid arginine, a building block of proteins, is produced from argininosuccinate, the molecule that carries the waste nitrogen collected earlier in the urea cycle. The arginine is later broken down into urea, which is excreted, and ornithine, which restarts the urea cycle.

How are changes in the ASL gene related to health conditions?

argininosuccinic aciduria - caused by mutations in the ASL gene

More than 30 different mutations in the ASL gene have been identified worldwide. In some cases, a short sequence of DNA is deleted from the gene. Other mutations replace one protein building block (amino acid) with another amino acid in the argininosuccinate lyase enzyme. In people of Arab descent, two common mutations replace the amino acid glutamine with a premature stop signal at position 116 (written as Gln116Ter or Q116X) or position 354 (written as Gln354Ter or Q354X) in the argininosuccinate lyase enzyme. Mutations in the ASL gene may result in an argininosuccinate lyase enzyme that is unstable or the wrong shape.

The shape of an enzyme affects its ability to control a chemical reaction. If the argininosuccinate lyase enzyme is misshapen or missing, it cannot fulfill its role in the urea cycle. Excess nitrogen is not converted to urea for excretion, and ammonia accumulates in the body. Ammonia is toxic, especially to the nervous system, so this accumulation causes neurological problems and other signs and symptoms of argininosuccinic aciduria.

Where is the ASL gene located?

Cytogenetic Location: 7q11.21

Molecular Location on chromosome 7: base pairs 66,075,789 to 66,093,343

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The ASL gene is located on the long (q) arm of chromosome 7 at position 11.21.

The ASL gene is located on the long (q) arm of chromosome 7 at position 11.21.

More precisely, the ASL gene is located from base pair 66,075,789 to base pair 66,093,343 on chromosome 7.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about ASL?

You and your healthcare professional may find the following resources about ASL helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the ASL gene or gene products?

  • Argininosuccinase
  • Arginosuccinase
  • arginosuccinate lyase

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding ASL?

aciduria ; amino acid ; ammonia ; arginine ; compound ; DNA ; enzyme ; excretion ; gene ; glutamine ; molecule ; nervous system ; neurological ; protein ; toxic ; urea

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Al-Sayed M, Alahmed S, Alsmadi O, Khalil H, Rashed MS, Imtiaz F, Meyer BF. Identification of a common novel mutation in Saudi patients with argininosuccinic aciduria. J Inherit Metab Dis. 2005;28(6):877-83. (
  • Biochemistry (fifth edition, 2002): Ammonium Ion is Converted into Urea in Most Terrestrial Vertebrates. (
  • Christodoulou J, Craig HJ, Walker DC, Weaving LS, Pearson CE, McInnes RR. Deletion hotspot in the argininosuccinate lyase gene: association with topoisomerase II and DNA polymerase alpha sites. Hum Mutat. 2006 Nov;27(11):1065-71. (
  • Linnebank M, Tschiedel E, Häberle J, Linnebank A, Willenbring H, Kleijer WJ, Koch HG. Argininosuccinate lyase (ASL) deficiency: mutation analysis in 27 patients and a completed structure of the human ASL gene. Hum Genet. 2002 Oct;111(4-5):350-9. Epub 2002 Aug 14. (
  • NCBI Gene (
  • Reid Sutton V, Pan Y, Davis EC, Craigen WJ. A mouse model of argininosuccinic aciduria: biochemical characterization. Mol Genet Metab. 2003 Jan;78(1):11-6. (
  • Tanaka T, Nagao M, Mori T, Tsutsumi H. A novel stop codon mutation (X465Y) in the argininosuccinate lyase gene in a patient with argininosuccinic aciduria. Tohoku J Exp Med. 2002 Oct;198(2):119-24. (
  • Turner MA, Simpson A, McInnes RR, Howell PL. Human argininosuccinate lyase: a structural basis for intragenic complementation. Proc Natl Acad Sci U S A. 1997 Aug 19;94(17):9063-8. (
  • Yu B, Howell PL. Intragenic complementation and the structure and function of argininosuccinate lyase. Cell Mol Life Sci. 2000 Oct;57(11):1637-51. Review. (
  • Yu B, Thompson GD, Yip P, Howell PL, Davidson AR. Mechanisms for intragenic complementation at the human argininosuccinate lyase locus. Biochemistry. 2001 Dec 25;40(51):15581-90. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: March 2007
Published: February 8, 2016