Histidine decarboxylase

Histidine decarboxylase (HDC) is the is_associated_with::enzyme that catalyzes the reaction that produces is_associated_with::histamine from is_associated_with::histidine with the help of vitamin B6 as follows:



In humans, the histidine decarboxylase enzyme is encoded by the HDC is_associated_with::gene.

Function
The is_associated_with::biogenic amine histamine is an important modulator of numerous physiologic processes, including is_associated_with::neurotransmission, gastric acid secretion, and smooth muscle tone. The biosynthesis of histamine from histidine is catalyzed by the enzyme L-histidine decarboxylase. This homodimeric enzyme is a is_associated_with::pyridoxal phosphate (PLP)-dependent decarboxylase and is highly specific for its histidine substrate.

Biosynthesis
In is_associated_with::bacteria, it is synthesised as a is_associated_with::proenzyme, PI. Cleavage of the proenzyme PI chain yields two subunits, alpha and beta, which arrange as a is_associated_with::hexamer, (alpha beta)6, by nonhydrolytic self-catalysis.

Clinical significance
Known inhibitors of histidine decarboxylase: is_associated_with::catechin, is_associated_with::tritoqualine an atypical is_associated_with::antihistamine.

Mutations in the gene for this enzyme have been observed in one family with is_associated_with::Tourette syndrome (TS) and are not thought to account for most cases of TS.