Biochemical basis of histamine

Histamine (biochem: 2-(1H-imidazol-4-yl)ethanamine) is a biogenic amine. It was discovered in 1911 and has a molecular mass of 111. Histamine is found as tissue hormone and neurotransmitter in animal organisms and also in plants as well as in bacteria. In animals (including humans) histamine plays a central role in allergic (IgE mediated) reactions and participates in the defence against foreign bodies.

Histamine is synthesised from the amino acid histidine through a pyridoxalphosphate-dependant decarboxylation using histidine carboxylase in a single phase reaction.

histamin_strukturThe most important function of histamine consists of its participation in the defence against exogenous substances and its pathological participation in the symptomatology of allergies and asthma. Here the histamine is responsible for itching and pain, smooth muscle contraction in the bronchia and large blood vessels, as well as vasodilation of smaller blood vessels related to erythema. Histamine also causes the release of adrenaline resulting in stronger cardiac contraction and a faster heart rate.

In the central nervous system histamine is involved in inducing vomiting as well as in the regulation of the sleep-wake rhythm through the activation of H1 receptors. It also acts as an antidepressant. Histamine also has appetite-suppressant properties and seems to be involved in the regulation of body temperature, the central control of blood pressure and sensitivity to pain.

In the gastrointestinal tract histamine has a regulatory function in the production of gastric acid and in gastrointestinal motility.

Sources:
Stryer, L., Biochemie, Specktrum Akademischer Verlag, 4. Auflage
Beliz, H.D., Lehrbuch der Lebensmittelchemie, Springer Verlag, 2001