Histamine N-methyltransferase

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Histamine N-methyltransferase
Histamine n-methyltransferase1.png
Crystallographic structure of human histamine N-methyltransferase.[1]
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols HNMT ; HMT; HNMT-S1; HNMT-S2
External IDs OMIM605238 HomoloGene5032 GeneCards: HNMT Gene
EC number
Species Human Mouse
Entrez 3176 140483
Ensembl ENSG00000150540 ENSMUSG00000026986
UniProt P50135 Q91VF2
RefSeq (mRNA) NM_001024074 NM_080462
RefSeq (protein) NP_001019245 NP_536710
Location (UCSC) Chr 2:
138.72 – 138.77 Mb
Chr 2:
24 – 24.05 Mb
PubMed search [1] [2]
histamine N-methyltransferase
EC number
CAS number 9029-80-5
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO

Histamine N-methyltransferase (HMT, HNMT) is an enzyme that in humans is encoded by the HNMT gene.[2]

Histamine N-methyltransferase is one of two enzymes involved in the metabolism of histamine, the other being diamine oxidase. Histamine N-methyltransferase catalyzes the methylation of histamine in the presence of S-adenosylmethionine (SAM) forming N-methylhistamine. HMT is present in most body tissues but is not present in serum.[3] Histamine N-methyltransferase is encoded by a single gene which has been mapped to chromosome 2.


In mammals, histamine is metabolized by two major pathways: N(tau)-methylation via histamine N-methyltransferase and oxidative deamination via diamine oxidase. This gene encodes the first enzyme which is found in the cytosol and uses S-adenosyl-L-methionine as the methyl donor. In the mammalian brain, the neurotransmitter activity of histamine is controlled by N(tau)-methylation as diamine oxidase is not found in the central nervous system. A common genetic polymorphism affects the activity levels of this gene product in red blood cells.[2]


  1. ^ PDB 1JQD; Horton JR, Sawada K, Nishibori M, Zhang X, Cheng X (September 2001). "Two polymorphic forms of human histamine methyltransferase: structural, thermal, and kinetic comparisons". Structure 9 (9): 837–49. doi:10.1016/S0969-2126(01)00643-8. PMID 11566133. 
  2. ^ a b "Entrez Gene: Histamine N-methyltransferase". 
  3. ^ Brown DD, Tomchick R, Axelrod J (November 1959). "The distribution and properties of a histamine-methylating enzyme" (PDF). J. Biol. Chem. 234 (11): 2948–50. PMID 13804910. 

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