Histidine ammonia-lyase

Histidine ammonia-lyase (EC 4.3.1.3, histidase, histidinase) is an enzyme that in humans is encoded by the HAL gene.^[5][6] It converts histidine into ammonia and urocanic acid. Its systematic name is L-histidine ammonia-lyase (urocanate-forming).

HAL
Identifiers
Aliases	HAL, HIS, HSTD, histidine ammonia-lyase, Histidine ammonia-lyase
External IDs	OMIM: 609457; MGI: 96010; HomoloGene: 68229; GeneCards: HAL; OMA:HAL - orthologs
Gene location (Human) Chr. Chromosome 12 (human)[1] Band 12q23.1 Start 95,972,662 bp[1] End 95,996,365 bp[1]
Gene location (Mouse) Chr. Chromosome 10 (mouse)[2] Band 10 C2|10 48.49 cM Start 93,324,630 bp[2] End 93,355,166 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in right lobe of liver human penis skin of thigh vulva blood oocyte skin of arm monocyte secondary oocyte skin of abdomen Top expressed in morula skin of external ear left lobe of liver lip skin of back lumbar spinal ganglion calvaria umbilical cord spermatid granulocyte More reference expression data BioGPS n/a
Gene ontology Molecular function catalytic activity lyase activity ammonia-lyase activity histidine ammonia-lyase activity Cellular component cytosol cytoplasm Biological process histidine metabolic process histidine catabolic process to glutamate and formate histidine catabolic process to glutamate and formamide histidine catabolic process Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 3034 15109 Ensembl ENSG00000084110 ENSMUSG00000020017 UniProt P42357 P35492 RefSeq (mRNA) NM_001258333 NM_001258334 NM_002108 NM_010401 RefSeq (protein) NP_001245262 NP_001245263 NP_002099 NP_034531 Location (UCSC) Chr 12: 95.97 – 96 Mb Chr 10: 93.32 – 93.36 Mb PubMed search [3] [4]
Wikidata
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histidine ammonia-lyase
Histidine ammonia-lyase homotetramer, Pseudomonas putida
Identifiers
EC no.	4.3.1.3
CAS no.	9013-75-6
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

Function

Histidine ammonia-lyase is a cytosolic enzyme catalyzing the first reaction in histidine catabolism, the nonoxidative deamination of L-histidine to trans-urocanic acid.^[5] 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.^[7]

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

Pathology

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

See also

• Phenylalanine ammonia-lyase, another enzyme that contains the MIO cofactor