Blood & Laboratory Values

Histidine – Function & Diseases

Histidine

Histidine is a basic amino acid that has an imidazole ring as an important functional group.

It is a semi-essential amino acid that plays a central role in the organism. For children in the growth phase and people with renal insufficiency , the need for histidine is so high that it can be classified as an essential amino acid for this group of people.

What is histidine?

Along with arginine and lysine , histidine is one of the few basic amino acids. At the same time, it is also an aromatic amino acid with its imidazole ring. It occurs in two optically active forms. The enantiomer L-histidine represents the actual proteinogenic amino acid.

D-histidine has no biological significance. In the following, the term histidine always means only L-histidine. In total, histidine contains six carbon atoms. It also has two nitrogen atoms in the imidazole ring. In addition to the obligatory nitrogen in the alpha-position amino group, there are therefore three nitrogen atoms in the molecule as a whole. Because of the imidazole ring, histidine has a basic reaction.

Histidine exists in two tautomeric forms as the hydrogen atom attached to nitrogen in the imidazole ring moves back and forth between the two nitrogen atoms. The special structure of the imidazole ring and the resulting basicity give the histidine-containing proteins buffering properties.

Function, effect & tasks

Histidine plays a central role in the organism. Since its isoelectric point is in the neutral range, histidine is the only amino acid that can function both as a proton acceptor and as a proton donor.

In addition to basic properties, it also has acidic properties. Because of this, histidine can participate in many enzymatic reactions associated with proton transfer. Their central role is expressed in the so-called catalytic triad. The catalytic triad is a sequence of amino acids aspartic acid , histidine, and serine that is commonly found in enzymes . This structural unit catalyzes protein breakdown through the hydrolytic cleavage of peptide bonds in proteins. Furthermore, histidine serves as a starting material for the red blood pigment hemoglobin.

Since it has good complexing properties, it forms complexes with iron within the histidine-containing proteins. This is how it occurs in ferritin and ensures its iron storage capacity within the organism. Due to its ability to bind to heavy metals, it also has a detoxifying effect on the body. Histidine also serves as a precursor to the synthesis of histamine . In this way, it strengthens the immune system , since histamine is involved in the defense against foreign substances.

Histidine is also a starting material for the production of glutamate . It is of great importance for the growth processes. It is therefore an essential amino acid for growing children and adolescents. It also supports wound healing and has an anti-inflammatory effect.

Formation, Occurrence, Properties & Optimal Values

As already mentioned, histidine is actually a non-essential amino acid that can be produced by the body itself. However, the yield of the synthesis is so low that it always has to be supplied with food to cover requirements. That is why today we prefer to speak of semi-essential amino acids. In growing children, however, external intake is essential because the growth process requires large amounts of histidine. The same applies to serious diseases such as renal insufficiency.

Healthy adults, however, get enough histidine from their diet. A histidine deficiency is rare in Central Europe and is only to be expected in the case of an extremely unbalanced diet. Chicken, salmon, nuts, soybeans, unpeeled rice, peas, milk and chicken eggs are particularly high in histidine. Since these products or components of these products are found in almost all foods, an adequate supply of histidine should generally be ensured. However, even with a lower intake of histidine, the body’s own production does not increase.

Diseases & Disorders

Due to the central role of histidine, its deficiency or a disturbed breakdown of histidine degradation products such as histamine can lead to various health problems. In the case of certain diseases, the histidine concentrations found in the organism are too low.

This applies to chronic renal insufficiency or rheumatoid arthritis . It was found that an increased intake of histidine has a positive effect on rheumatoid arthritis. As part of its central role in metabolism, it has an anti-inflammatory effect, so that the strong inflammatory processes are severely restricted. The need for histidine is also increased in the case of severe injuries and trauma. Too low a concentration leads to delayed wound healing . If too little histidine is supplied during the growth phase, growth disorders occur. Histidine is a good radical scavenger and therefore also has the potential to slow down degenerative processes.

Furthermore, the positive effect of histidine on high blood pressure and infections was recognized. Blood pressure can be lowered in the long term and the duration of a cold can be significantly reduced. There is a genetic disease in which the breakdown of histidine is disturbed. However, the autosomal recessive hereditary disease known as histidinemia usually does not cause any symptoms, so that treatment is usually not necessary. However, under unusual conditions, central nervous system symptoms may present. A low histidine diet is then recommended. In patients with stress , anxiety disorders or schizophreniavery high histidine concentrations were found in some cases.

Overall, however, the increased concentration of a synthetic product of histidine, histamine, plays a greater role in disease processes. Histamine is an active ingredient that causes a wide range of symptoms in the event of breakdown disorders, such as autoimmune disorders , allergies , cardiovascular diseases or gastrointestinal disorders. For treatment, foods rich in histamine should be avoided. However, foods with a high histamine content also contain a lot of histidine.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.