Biology:Histidine ammonia-lyase

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A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

Histidine ammonia-lyase (EC 4.3.1.3, histidase, histidinase) is an enzyme that in humans is encoded by the HAL gene.[1][2] It converts histidine into ammonia and urocanic acid. Its systematic name is L-histidine ammonia-lyase (urocanate-forming).

Function

Proposed autocatalytic formation of MIO cofactor in another enzyme, phenylalanine ammonia-lyase, from the tripeptide Ala-Ser-Gly by two water elimination steps.

Histidine ammonia-lyase is a cytosolic enzyme catalyzing the first reaction in histidine catabolism, the nonoxidative deamination of L-histidine to trans-urocanic acid.[1] The reaction is catalyzed by 3,5-dihydro-5-methyldiene-4H-imidazol-4-one (MIO), an electrophilic cofactor which is formed autocatalytically by cyclization of the protein backbone of the enzyme.[3]

Pathology

Mutations in the gene for histidase are associated with histidinemia and urocanic aciduria.

See also

References

  1. Jump up to: 1.0 1.1 "Entrez Gene: histidine ammonia-lyase". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=3034. 
  2. "Molecular cloning and structural characterization of the human histidase gene (HAL)". Genomics 29 (1): 98–104. September 1995. doi:10.1006/geno.1995.1219. PMID 8530107. 
  3. Schwede, TF; Rétey, J; Schulz, GE (Apr 27, 1999). "Crystal structure of histidine ammonia-lyase revealing a novel polypeptide modification as the catalytic electrophile.". Biochemistry 38 (17): 5355–5361. doi:10.1021/bi982929q. PMID 10220322. 

Further reading

External links

This article incorporates text from the United States National Library of Medicine, which is in the public domain.