Threonin

Threonine, with the chemical formula C4H9NO3, is one of the 20 standard amino acids used to build proteins. It exists in two mirror-image forms, L-threonine and D-threonine; in biology, proteins are composed almost exclusively of the L enantiomer. Threonine is an essential (indispensable) amino acid for adults, meaning humans cannot synthesize it and must obtain it from the diet. Requirements vary by age and health status.

Dietary sources include animal products such as meat, fish, eggs, and dairy, as well as plant foods like soy, lentils, nuts, seeds, and grains. The amino acid profile of a person’s diet influences threonine availability, and it is commonly included in complete protein sources or dietary supplements when necessary.

In the body, threonine participates in protein synthesis and supports several physiological processes, including the maintenance of gut mucosa, immune function, and the synthesis of glycine and serine as part of broader metabolic networks. It also contributes to the formation of collagen and other structural proteins.

Codons in the genetic code that specify threonine are ACU, ACC, ACA, and ACG. In medicine and nutrition, threonine is used in specialized nutritional formulations, particularly for individuals with malnutrition or those requiring parenteral nutrition. Excessive intake from supplements can cause digestive upset and disrupt amino acid balance.