histaminNmetyltransferase

Histamine N-methyltransferase (HNMT) is an enzyme that plays a crucial role in the metabolism of histamine, a biogenic amine involved in various physiological processes including immune response, neurotransmission, and gastric acid secretion. HNMT catalyzes the transfer of a methyl group from S-adenosyl methionine (SAM) to the imidazole ring of histamine, forming N-methylhistamine. This enzymatic reaction effectively inactivates histamine, reducing its biological activity.

HNMT is widely distributed in the human body, with particularly high concentrations found in the liver, kidneys, and lungs. Its presence in these organs suggests its importance in detoxifying circulating histamine and regulating its levels in different tissues. The enzyme is also found in the brain, where histamine acts as a neurotransmitter, and in cells of the immune system, such as mast cells and basophils, which release histamine during allergic reactions.

Genetic variations in the HNMT gene have been associated with differences in enzyme activity and histamine levels, potentially influencing susceptibility to certain conditions like allergies and asthma. Understanding the function and regulation of HNMT is therefore important for comprehending histamine's role in health and disease, and it has become a target for therapeutic interventions aimed at modulating histamine signaling.