Histamine N-methyltransferase

1JQD, 1JQE, 2AOT, 2AOU, 2AOV, 2AOW, 2AOX3176140483ENSG00000150540ENSMUSG00000026986P50135Q91VF2NM_001024074NM_001024075NM_006895NM_080462NP_001019245NP_001019246NP_008826NP_536710Histamine N-methyltransferase (HMT, HNMT) is an enzyme that in humans is encoded by the HNMT gene. Histamine N-methyltransferase (HMT, HNMT) is an enzyme that in humans is encoded by the HNMT gene. 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. 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. This article incorporates text from the United States National Library of Medicine, which is in the public domain.