Histamine and its physiological functions
Histamine is a type of biogenic tissue amine – L-histidine decarboxylase (HDC) and the cofactor pyridoxal 5’-phosphate or the active form of vitamin B6 mediate the conversion of histidine into histamine (its chemical reaction is represented in figure 1). The key enzymes such as diamine oxidase (DAO) and histamine N-methyltransferase (HNMT) degrade histamine into different by-products.
As per the International Union of Pure and Applied Chemistry (IUPAC)nomenclature, the chemical name of histamine is 2-(1H-imidazol-4-yl) ethanamine.
Essentially, the biogenic amines such as histamine, tyramine, putrescine and cadaverine at low concentrations have been reported to possess hazardous adverse effects on the human body. The storage of histamine is principally in lymph nodes, basophils, mast cells, gastric enterochromaffin cells and thymus. There are four histamine receptors, namely, H1, H2, H3 and H4, distributed in various parts of the human body. Histamine binds with respective receptors and displays the pharmacological effects.