Histidine

Histidine is an amino acid that is used in the biosynthesis of proteins. It contains an amino group, a carboxyl group, and a side chain imidazole, making it a basic and polar amino acid. It is essential in humans, meaning the body cannot synthesize it and it must be ingested. Histidine was first isolated by German physician Albrecht Kossel in 1896.

Structure

Histidine is a alpha-amino acid that includes an imidazole functional group. It is one of the 23 proteinogenic amino acids. Its codons are CAU and CAC.

Biosynthesis

In bacteria and plants, histidine is synthesized from the sugar derivative phosphoribosyl pyrophosphate (PRPP). The process involves nine enzyme-catalyzed reactions and is regulated by the concentration of histidine itself.

Function

Histidine plays a critical role in the catalytic site of enzymes. The imidazole side chain has the ability to switch between protonated and unprotonated states, which allows histidine to participate in acid-base catalysis. In addition, histidine is involved in the regulation of the pH levels of bodily fluids.

Histidine is also needed for growth and the repair of tissues, as well as the maintenance of the myelin sheaths that protect nerve cells. It is further used to manufacture both red and white blood cells.

Dietary Sources

Histidine is found in a wide variety of foods, including meat, poultry, fish, dairy, and certain types of grain. It is also available as a dietary supplement.

Deficiency

Histidine deficiency can lead to symptoms such as eczema, inflammation of the skin, and even neurological issues. It is rare, but can occur in people with a genetic disorder that affects histidine absorption.

See Also

• Amino acid
• Protein biosynthesis
• Enzyme catalysis
• Albrecht Kossel

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