In mammals, histamine is an important biogenic amine with regulatory roles in neurotransmission, gastric acid secretion and immune response.

The enzyme employs a pyridoxal 5'-phosphate (PLP) cofactor, in similarity to many amino acid decarboxylases.

This processing consists of truncating much of the protein's C-terminal chain, reducing the peptide molecular weight to 54 kDa.

Histidine decarboxylase exists as a homodimer, with several amino acids from the respective opposing chain stabilizing the HDC active site.

[10] HDC decarboxylates histidine through the use of a PLP cofactor initially bound in a Schiff base to lysine 305.

H1 modulates several functions of the central and peripheral nervous system, including circadian rhythm, body temperature and appetite.

Typical antihistamines block specific histamine receptors, depending on what physiological purpose they serve.

Tritoqualine, as well as various catechins, such as epigallocatechin-3-gallate, a major component of green tea, have been shown to target HDC and histamine-producing cells, reducing histamine levels and providing anti-inflammatory, anti-tumoral, and anti-angiogenic effects.

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