HAL gene

histidine ammonia-lyase

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

At least four mutations in the HAL gene have been found to cause histidinemia. All of these mutations change single amino acids in the histidase enzyme. These mutations are thought to decrease or eliminate enzyme activity, resulting in an inability to break down histidine. Histidine that is not broken down accumulates in the blood, but it typically causes no health problems.

Cytogenetic Location: 12q23.1, which is the long (q) arm of chromosome 12 at position 23.1

Molecular Location: base pairs 95,972,662 to 95,996,365 on chromosome 12 (Homo sapiens Annotation Release 108, GRCh38.p7) (NCBI)

Cytogenetic Location: 12q23.1, which is the long (q) arm of chromosome 12 at position 23.1
  • HIS
  • histidase
  • HSTD
  • HUTH_HUMAN