Amino acid of Histidine

Histidine was first isolated in 1896 from various proteins. It is an essential amino acid for humans. Histamine is the product of the alpha-decarboxylation of the proteinogenic amino acid histidine.

Histamine plays several important roles in human metabolism, among them serving as the signaling compound for the allergic response.

As a signaling compound, it is normally present in the human body, but its location and concentration are carefully regulated. Histidine is used by many proteins as a regulatory mechanism, changing the conformation and behavior of the polypeptide in acid regions such as the late endosome or lysosome.

Histidine is needed for growth and for repair of human tissues and is converted to a substance that stimulates the secretion of hydrochloric acid in the stomach to facilitate gastric function.

Most of the histidine processed in the body is derived from the diet. Natural sources of histidine include beans, dairy products, eggs, fish, meat nuts, seeds, soy and whey.
Amino acid of Histidine

Histamine in human body

Histamine is a naturally occurring compound synthesized in the body. It is a low molecular weight biogenic amine. It has been identified as a toxic agent which causes allergic reactions.

It is derived from amino acid histidine by the action of histidine decarboxylase. Histamine is found within granules of mast cells. basophils and platelets. It is concentrated especially in skin, gastrointestinal tract and lung.

Indigenous histamine is produced in the human body mainly in mast cells and is released as a result of response to allergens.

Mast cells release histamine in response to a number of stimuli, including mechanical stimulation, anaphylatoxins formed from complement and certain neuropeptides.

The mechanisms of histamine toxicity involves mediators known as histamine receptors such are responsible for the development of the various symptoms.

Histamines, one in the bloodstream has a number of effects. Histamine relaxes the smooth muscle of the arterioles leading to the wounded area, so increasing its blood flow.

It causes the cells of the capillary walls to draw away from one another, so that the capillaries become leaky. More plasma escapes from capillaries and collects in the site of the wound. The fluid causes the site of the wound to swell and become warm.

Allergic reactions to foods contain histamine depend not only how much histamine is, but also on individual threshold and the ability to breakdown histamine.
Histamine in human body

Histamine Poisoning

Allergy like food intoxication is an adverse reaction to a food or food component occurring as result of the ingestion of chemical mediators of allergic disease.

Unusual diets can sometimes result in intoxication from chemicals that would normally be considered safe and desirable.

The only example of this type of reaction is histamine poisoning, also known as ‘scombroid fish poisoning,’ which is commonly associated with consumption of spoiled tuna, mackerel, mahi-mahi and other fish.

Histamine also been reported in connection with non-fish fermented food like cheeses and sauerkraut.

Following the ingestion of food containing high level of histamine, occurs with variety of symptoms. The primary symptoms are cutaneous – rash, urticaria, oedema, localized inflammation, gastro-intestinal – nausea, vomiting, diarrhea, hemodynamic – hypotension and neurological – headache, tingling, burning, itching.

Histamine production in foods is by the decarboxylation of histidine though a reaction catalyzed by the enzyme histidine decarboxylase.

Histamine poisoning is an intoxication, so the incubation period is rather short, ranging from several minutes to a few hours after ingestion of the contaminated fish.
Histamine Poisoning