EC - Histidine ammonia-lyase

  IntEnz view ENZYME view

IntEnz Enzyme Nomenclature


Accepted name:
histidine ammonia-lyase
Other names:
histidine α-deaminase
L-histidine ammonia-lyase
Systematic name:
L-histidine ammonia-lyase (urocanate-forming)



This enzyme is a member of the aromatic amino acid lyase family, other members of which are EC (tyrosine ammonia-lyase), EC (phenylalanine ammonia-lyase) and EC (phenylalanine/tyrosine ammonia-lyase). The enzyme contains the cofactor 3,5-dihydro-5-methylidene-4H-imidazol-4-one (MIO), which is common to this family [4]. This unique cofactor is formed autocatalytically by cyclization and dehydration of the three amino-acid residues alanine, serine and glycine [5]. This enzyme catalyses the first step in the degradation of histidine and the product, urocanic acid, is further metabolized to glutamate [2,3].

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , NIST 74 , UniPathway
Protein domains and families: PROSITE:PDOC00424
Structural data: CSA , EC2PDB
Gene Ontology: GO:0004397
CAS Registry Number: 9013-75-6
UniProtKB/Swiss-Prot: (203) [show] [UniProt]


  1. Mehler, A.H. and Tabor, H.
    Deamination of histidine to form urocanic acid in liver.
    J. Biol. Chem. 201 : 775-784 (1953). [PMID: 13061415]
  2. Watts, K.T., Mijts, B.N., Lee, P.C., Manning, A.J. and Schmidt-Dannert, C.
    Discovery of a substrate selectivity switch in tyrosine ammonia-lyase, a member of the aromatic amino acid lyase family.
    Chem. Biol. 13 : 1317-1326 (2006). [PMID: 17185227]
  3. Poppe, L. and Rétey, J.
    Friedel-Crafts-type mechanism for the enzymatic elimination of ammonia from histidine and phenylalanine.
    Angew. Chem. Int. Ed. Engl. 44 : 3668-3688 (2005). [PMID: 15906398]
  4. Louie, G.V., Bowman, M.E., Moffitt, M.C., Baiga, T.J., Moore, B.S. and Noel, J.P.
    Structural determinants and modulation of substrate specificity in phenylalanine-tyrosine ammonia-lyases.
    Chem. Biol. 13 : 1327-1338 (2006). [PMID: 17185228]
  5. Schwede, T.F., Rétey, J. and Schulz, G.E.
    Crystal structure of histidine ammonia-lyase revealing a novel polypeptide modification as the catalytic electrophile.
    Biochemistry 38 : 5355-5361 (1999). [PMID: 10220322]

[EC created 1961, modified 2008]