Histidiinidekarboksylaasin

Histidiinidekarboksylaasin, also known as histidine decarboxylase (HDC), is an enzyme with the systematic name L-histidine carboxy-lyase. It catalyzes the decarboxylation of histidine to form histamine. This reaction is a crucial step in the biosynthesis of histamine, a biogenic amine involved in various physiological processes in humans and other organisms.

The enzyme is widely distributed in nature, found in mammals, bacteria, fungi, and plants. In mammals, HDC is primarily found in enterochromaffin-like cells of the gastric mucosa, mast cells, basophils, and neurons. Its activity is essential for the production of histamine, which acts as a neurotransmitter, a mediator of allergic and inflammatory responses, and plays a role in gastric acid secretion.

The reaction catalyzed by HDC involves the removal of a carboxyl group from the alpha-carbon of histidine. This process requires pyridoxal phosphate (PLP) as a cofactor, which forms a Schiff base with the amino group of histidine, facilitating the decarboxylation reaction. The gene encoding HDC is located on chromosome 15 in humans.

Dysregulation of HDC activity has been implicated in various pathological conditions. For example, increased HDC expression and histamine levels are associated with certain types of cancer, such as gastric cancer. Conversely, deficiencies in HDC can lead to altered histamine signaling, potentially affecting neurological functions and immune responses. Research into HDC continues to explore its therapeutic potential for conditions related to histamine imbalance.