Lthreonine

L-threonine is one of the 20 standard amino acids and the L-enantiomer is the form incorporated into human proteins. It is an essential amino acid in humans, meaning the body cannot synthesize it in adequate amounts and it must be obtained from the diet. The threonine side chain contains a hydroxyl group, giving it polar, hydrophilic properties.

Threonine is encoded by the genetic codons ACU, ACC, ACA, and ACG. It is widely distributed in protein-rich foods and is found in dairy products, meats, eggs, fish, soy products, legumes, nuts, and grains. In many dietary patterns, threonine is an important component of the overall amino acid balance.

Physiological roles include incorporation into body proteins and involvement in mucin production, where threonine-rich glycoproteins contribute to protective mucus layers in the gut and other tissues. It also serves as a metabolic substrate that can be degraded to feed into energy pathways.

Deficiency is uncommon in developed diets but can occur with severe malnutrition or restrictive diets and can manifest as growth retardation, weight loss, or immune dysfunction. Excess intake from supplements may alter amino acid balance and is generally avoided; upper intake levels are not broadly established.

Industrial production of L-threonine is achieved primarily by microbial fermentation using carbohydrate substrates and engineered strains, followed by purification and crystallization. The product is marketed as free L-threonine or in salt forms for use in human nutrition, medical formulations, and animal feeds.