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HAL gene
URL of this page: https://medlineplus.gov/genetics/gene/hal/

HAL gene

histidine ammonia-lyase

Normal Function

The HAL gene provides instructions for making an enzyme called histidase. Histidase breaks down the amino acid histidine, which acts as a building block for many different proteins. Histidase is active (expressed) primarily in the liver and the skin. This enzyme breaks down histidine to a molecule called urocanic acid. During digestion, urocanic acid is broken down in the liver to form another amino acid called glutamate. In the skin, urocanic acid is involved in the response to ultraviolet (UV) light.

Health Conditions Related to Genetic Changes

Histidinemia

Several variants (also called mutations) in the HAL gene have been found to cause an inherited condition called histidinemia. People with histidinemia have high levels of histidine in the blood, urine, and the fluid that surrounds the brain and spinal cord (cerebrospinal fluid). Most of the variants change single amino acids in the histidase enzyme and are thought to decrease or eliminate the enzyme's activity. A decrease in histidase activity interferes with the body's ability to break down histidine. Histidine then builds up in the blood, urine, and cerebrospinal fluid. Rarely, people with histidinemia have intellectual disabilities, learning disabilities, or behavioral complications. Having a medical complication during or soon after birth might increase the risk of developmental problems in people with histidinemia.

More About This Health Condition

Other Names for This Gene

  • HIS
  • histidase
  • HSTD

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases

References

  • Brosco JP, Sanders LM, Dharia R, Guez G, Feudtner C. The lure of treatment: expanded newborn screening and the curious case of histidinemia. Pediatrics. 2010 Mar;125(3):417-9. doi: 10.1542/peds.2009-2060. Epub 2010 Feb 15. No abstract available. Citation on PubMed
  • Brosnan ME, Brosnan JT. Histidine Metabolism and Function. J Nutr. 2020 Oct 1;150(Suppl 1):2570S-2575S. doi: 10.1093/jn/nxaa079. Citation on PubMed
  • Eckhart L, Schmidt M, Mildner M, Mlitz V, Abtin A, Ballaun C, Fischer H, Mrass P, Tschachler E. Histidase expression in human epidermal keratinocytes: regulation by differentiation status and all-trans retinoic acid. J Dermatol Sci. 2008 Jun;50(3):209-15. doi: 10.1016/j.jdermsci.2007.12.009. Epub 2008 Feb 15. Citation on PubMed
  • Kawai Y, Moriyama A, Asai K, Coleman-Campbell CM, Sumi S, Morishita H, Suchi M. Molecular characterization of histidinemia: identification of four missense mutations in the histidase gene. Hum Genet. 2005 Apr;116(5):340-6. doi: 10.1007/s00439-004-1232-5. Epub 2005 Jan 27. Erratum In: Hum Genet. 2005 Dec;118(3-4):531-2. Citation on PubMed
  • Kessler AT, Raja A. Biochemistry, Histidine. 2023 Jul 30. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from http://www.ncbi.nlm.nih.gov/books/NBK538201/ Citation on PubMed
  • Levy HL, Shih VE, Madigan PM. Routine newborn screening for histidinemia. Clinical and biochemical results. N Engl J Med. 1974 Dec 5;291(23):1214-9. doi: 10.1056/NEJM197412052912303. No abstract available. Citation on PubMed
  • Moro J, Tome D, Schmidely P, Demersay TC, Azzout-Marniche D. Histidine: A Systematic Review on Metabolism and Physiological Effects in Human and Different Animal Species. Nutrients. 2020 May 14;12(5):1414. doi: 10.3390/nu12051414. Citation on PubMed
  • Suchi M, Sano H, Mizuno H, Wada Y. Molecular cloning and structural characterization of the human histidase gene (HAL). Genomics. 1995 Sep 1;29(1):98-104. doi: 10.1006/geno.1995.1219. Citation on PubMed

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